RESUMEN
The objective of this study was to investigate the possible modulatory role of endogenous nitric oxide (NO) production on the urethral striated muscle (USM) function in the sheep urethra. Significant NO synthase (NOS) activity was measured in both the particulate and cytosolic fractions of USM homogenates. NOS activity was calcium-dependent and showed greater inhibition by NOS inhibitors selective of the neural NOS isoform (nNOS). nNOS immunoreactivity was present in intramural nerves as well as in the sarcolemma of some striated fibers, being denser at the neuromuscular junction (NMJ). Double immunolabeling showed co-localization of nNOS with both alpha-bungarotoxin and choline acetyltransferase, at the USM endplates. For the first time, functional data support a role of NO on the USM contractility "in vitro," which became evident following partial nicotinic receptor inactivation with low concentrations of D-tubocurarine. Only under D-tubocurarine (0.25 microM) treatment, different NOS inhibitors, specially N(G)-propyl-L-arginine, as well as the guanylate cyclase inhibitor ODQ, all showed a significant enhancing effect on contractions induced by electrical field stimulation of intrinsic somatic nerves. These data suggest that local production of NO at the urethral NMJ may modulate release and/or action of acetylcholine on motor endplates by cyclic GMP-mediated effects. This modulatory action could be especially relevant when neuromuscular transmission at the USM is impaired.
Asunto(s)
Músculo Esquelético/fisiología , Proteínas del Tejido Nervioso/análisis , Óxido Nítrico Sintasa/análisis , Óxido Nítrico/biosíntesis , Receptores Nicotínicos/efectos de los fármacos , Uretra/fisiología , Animales , Colina O-Acetiltransferasa/metabolismo , Estimulación Eléctrica , Femenino , Guanilato Ciclasa/fisiología , Placa Motora/enzimología , Unión Neuromuscular , Óxido Nítrico/fisiología , Óxido Nítrico Sintasa de Tipo I , Ovinos , Distribución Tisular , Tubocurarina/farmacología , Fenómenos Fisiológicos del Sistema UrinarioRESUMEN
We examined the contribution of K+ channels to the relaxation responses induced by different redox forms of nitric oxide (NO., NO- and NO+) in comparison with those evoked by electrical field stimulation (EFS) of nitrergic nerves in the sheep urethra. K+ channel blockers with different selectivity profile were used. Sodium nitroprusside (SNP) and different S-nitrosothiols were used as NO+ donors, Angeli's salt as an NO- donor and nitroglycerin (GTN) was chosen as a representative compound known to require metabolic activation in the target tissue. Pure NO gas was used to prepare NO. solutions. Relaxation evoked by EFS of nitrergic nerves or by exogenous NO was not inhibited by any of the K+ channel blockers, but was enhanced by 4-aminopyridine [inhibitor of voltage-dependent K+ (KV) channels]. This suggests that, whereas K+ channel activation and hyperpolarization of the postsynaptic membrane do not contribute to relaxation, prejunctional modulation of the nitrergic neurotransmission by Kv channels may be relevant. Relaxation induced by NO+ or NO- donors was not affected by K+ channel blockade with the following exceptions: glybenclamide, a blocker of ATP-sensitive K+ channels (KATP), enhanced responses to SNP and Angeli's salt, 4-aminopyridine inhibited relaxation evoked by Angeli's salt and GTN, and charybdotoxin, a blocker of large-conductance, Ca2+-activated K+ channels (BKCa) inhibited those induced by the S-nitrosothiol S-nitrosoglutathione. These results do not suggest the existence of a general mechanism of action on K+ channels for compounds releasing either NO+ or NO- in the sheep urethra. None of the K+ channel blockers affected relaxation induced by the membrane-permeable analogue of cGMP, 8-bromo-cGMP. However, the fact that the addition of the phosphodiesterase inhibitor zaprinast (0.1 mM) enhanced the relaxation to Angeli's salt, while preventing the inhibition induced by 4-aminopyridine, suggests that involvement of guanylate cyclase activation in the action of NO donors on K+ channels can not be excluded. Accordingly, the guanylate cyclase inhibitors 1H-[1,2,4]-oxadiazole-[4,3-a]-quinoxalin-1-one (ODQ, 10 microM) and 4H-8-bromo-1,2,4-oxadiazolo(3,4-d)benz(b)(1,4)oxazin-1-one (NS 2028, 10 microM) almost abolished relaxations to EFS and Angeli's salt. In contrast, ODQ only moderately inhibited relaxations to NO.. In addition, the NO scavenger 2-(4-carboxyphenyl)-4,4,5,5-tetramethyl imidazoline-1-oxyl 3-oxide (carboxy-PTIO) effectively inhibited responses to NO. whilst not affecting those to EFS or NO-, suggesting a close similarity between the nitrergic transmitter and nitroxyl ion. We conclude that nitrergic relaxation induced either by the endogenous transmitter or by exogenous NO donors in the ovine urethra is not mediated by postsynaptic alterations in the K+ conductance; only a prejunctional modulation through Kv channels seems to be significant. In addition, the production and/or release of alternative redox forms of NO, such as NO-, may be involved in neurotransmission processes in the urethra.
Asunto(s)
Relajación Muscular/fisiología , Músculo Liso/fisiología , Neuronas Nitrérgicas/fisiología , Óxido Nítrico/fisiología , Canales de Potasio/fisiología , Uretra/fisiología , Animales , Relación Dosis-Respuesta a Droga , Estimulación Eléctrica , Femenino , Relajación Muscular/efectos de los fármacos , Músculo Liso/efectos de los fármacos , Neuronas Nitrérgicas/efectos de los fármacos , Óxido Nítrico/metabolismo , Óxido Nítrico/farmacología , Donantes de Óxido Nítrico/farmacología , Oxidación-Reducción , Bloqueadores de los Canales de Potasio/farmacología , Ovinos , Uretra/efectos de los fármacos , Vasodilatadores/farmacologíaRESUMEN
PURPOSE: We prospectively evaluated the safety and efficacy of intrarectal lidocaine gel as anesthesia during transrectal prostate biopsy. MATERIALS AND METHODS: Of 63 consecutive men undergoing transrectal prostate biopsy 50 who qualified were enrolled in this study. Indications for the procedure were an abnormal prostate on digital rectal examination and/or elevated serum prostate specific antigen. Patients were randomized into group 1-25 who received 10 cc of 2% intrarectal lidocaine 10 minutes before the procedure and group 2-25 controls. No narcotics, sedation or analgesia was given. Pain during biopsy was assessed using a 10-point linear visual analog pain scale. RESULTS: In groups 1 and 2 median patient age was 63 and 66 years (p = 0.139), and median prostate specific antigen was 6.04 (range 1.07 to 263) and 7.24 (range 1.34 to 51.82) ng./ml. (p = 0.337). Digital rectal examination was normal and abnormal in 17 and 15 group 1, and in 8 and 10 group 2 patients, respectively. Ultrasound showed a median prostate volume of 43.6 cc (range 15.3 to 124) in group 1 and 40.3 (range 19.8 to 132) in group 2 (p = 0.710). Final histological results revealed prostate cancer in 7 men (28%) in each group. The median pain score during transrectal prostate biopsy was 2 (range 1 to 5) and 5 (range 1 to 7) in groups 1 and 2, respectively (p = 0.00001). No adverse events were noted. CONCLUSIONS: Intrarectal lidocaine gel is a simple, safe and efficacious method of providing satisfactory anesthesia in men undergoing transrectal prostate biopsy. We recommend its routine administration in all patients during this procedure.
Asunto(s)
Analgesia/métodos , Biopsia/métodos , Lidocaína/administración & dosificación , Próstata/patología , Administración Rectal , Anciano , Anestesia/métodos , Geles , Humanos , Masculino , Persona de Mediana Edad , Dimensión del Dolor , Estudios Prospectivos , Antígeno Prostático Específico/sangre , Neoplasias de la Próstata/patología , SeguridadRESUMEN
1. In the present work we have characterized the relaxant response induced by light stimulation (LS) in the lower urinary tract from sheep, pig and rat, establishing its relationship with nitrergic neurotransmission. 2. Urethral, but not detrusor, preparations showed pronounced photo-relaxation (PR) which declined progressively following repetitive LS. Sheep urethral PR was again restored either spontaneously or (to a greater extent) by exogenous nitric oxide (NO) addition and by electrical field stimulation (EFS) of intrinsic nitrergic nerves. 3. Greater NO generation was detected from sheep urethral than from detrusor homogenates following illumination. 4. Sheep urethral PR was inhibited by oxyhaemoglobin, but not by methaemoglobin, carboxy-PTIO, extracellular superoxide anion generators or superoxide dismutase. Guanylyl cyclase but not adenylyl cyclase activation mediates urethral relaxation to LS. 5. Urethral PR was more resistant to inhibition by L-thiocitrulline than EFS-induced responses, although this agent prevented PR restoration by high-frequency EFS. 6. Urethral PR was TTX insensitive and partially modified in high-K+ solutions. Cold storage for 24 h greatly impaired urethral PR, although it was restored by high-frequency EFS. 7. Repetitive exposure to LS, EFS or exogenous NO induced changes in the shape of the EFS-induced nitrergic relaxation, possibly by pre-synaptic mechanisms. 8. In conclusion, we suggest the presence of an endogenous, photo-labile, nitro-compound store in the urethra, which seems to be replenished by neural nitric oxide synthase activity, indicating a close functional relationship with the nitrergic neurotransmitter.
Asunto(s)
Luz , Relajación Muscular/efectos de la radiación , Músculo Liso/efectos de la radiación , Óxido Nítrico/metabolismo , Transmisión Sináptica/efectos de la radiación , Uretra/efectos de la radiación , Adenina/análogos & derivados , Adenina/farmacología , Animales , Citrulina/análogos & derivados , Citrulina/farmacología , Frío , Técnicas de Cultivo , Estimulación Eléctrica , Inhibidores Enzimáticos/farmacología , Femenino , Relajación Muscular/efectos de los fármacos , Relajación Muscular/fisiología , Músculo Liso/efectos de los fármacos , Músculo Liso/inervación , Músculo Liso/metabolismo , Óxido Nítrico/antagonistas & inhibidores , Óxido Nítrico/farmacología , Oxadiazoles/farmacología , Oxihemoglobinas/farmacología , Inhibidores de Fosfodiesterasa/farmacología , Estimulación Luminosa , Potasio/farmacología , Purinonas/farmacología , Quinoxalinas/farmacología , Ratas , Ratas Wistar , Ovinos , Superóxidos/metabolismo , Porcinos , Transmisión Sináptica/efectos de los fármacos , Tetrodotoxina/farmacología , Tiourea/análogos & derivados , Tiourea/farmacología , Factores de Tiempo , Uretra/efectos de los fármacosRESUMEN
The effects of superoxide anion generators, the nitric oxide (NO) scavenger 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoine-1-oxyl 3-oxide (carboxy-PTIO), the specific guanylate cyclase inhibitor 1H-[1,2,4]-oxadiazole-[4,3-a]-quinoxalin-1-one (ODQ), and thiol modulating agents were investigated on relaxations induced by nitrergic stimulation and exogenous NO addition in the sheep urethra. Methylene blue (MB, 10 microM), pyrogallol (0.1 mM) and xanthine (X, 0.1 mM)/xanthine oxidase (XO, 0.1 u ml(-1)) inhibited NO-mediated relaxations, without affecting those induced by nitrergic stimulation. This resistance was not diminished following inhibition of endogenous Cu/Zn superoxide dismutase (Cu/Zn SOD) with diethyldithiocarbamic acid (DETCA, 3 mM), which almost abolished tissue SOD activity. Carboxy-PTIO (0.1 - 0.5 mM) inhibited NO-mediated relaxations but had no effect on responses to nitrergic stimulation, which were not changed by treatment with ascorbate oxidase (2 u ml(-1)). Relaxations to NO were reduced, but not abolished, by ODQ (10 microM), while nitrergic responses were completely blocked. The thiol modulators, ethacrynic acid (0.1 mM), diamide (1.5 mM), or 5,5'-dithio-bis (2-nitrobenzoic acid) (DTNB, 0. 5 mM), and subsequent treatment with dithiothreitol (DTT, 2 mM) had no effect on responses to nitrergic stimulation or NO. In contrast, N-ethylmaleimide (NEM, 0.2 mM) markedly inhibited both relaxations. L-cysteine (L-cys, 0.1 mM) had no effect on responses to NO, while it inhibited those to nitrergic stimulation, in a Cu/Zn SOD-independent manner. Our results do not support the view that the urethral nitrergic transmitter is free NO, and the possibility that another compound is acting as mediator still remains open. British Journal of Pharmacology (2000) 129, 53 - 62
Asunto(s)
Músculo Liso/fisiología , Óxido Nítrico/farmacología , Óxido Nítrico/fisiología , Compuestos de Sulfhidrilo/metabolismo , Superóxidos/metabolismo , Transmisión Sináptica/fisiología , Uretra/efectos de los fármacos , Animales , Ascorbato Oxidasa/metabolismo , Benzoatos/farmacología , Ditiocarba/farmacología , Estimulación Eléctrica , Inhibidores Enzimáticos/farmacología , Femenino , Guanilato Ciclasa/antagonistas & inhibidores , Imidazoles/farmacología , Técnicas In Vitro , Contracción Muscular/efectos de los fármacos , Contracción Muscular/fisiología , Relajación Muscular/efectos de los fármacos , Relajación Muscular/fisiología , Músculo Liso/efectos de los fármacos , Músculo Liso/enzimología , Oxadiazoles/farmacología , Quinoxalinas/farmacología , Ovinos , Superóxido Dismutasa/metabolismo , Transmisión Sináptica/efectos de los fármacos , Uretra/enzimologíaRESUMEN
PURPOSE: We evaluate the feasibility, effectiveness and role of transperineal prostate block in providing anesthesia during minimally invasive radio frequency thermal therapy of the prostate. MATERIALS AND METHODS: A total of 38 consecutive patients undergoing transurethral needle ablation for symptomatic benign prostatic hyperplasia were entered in this prospective study. All patients received transperineal prostatic block as the main method of anesthesia. A mixture of equal volumes of 1% lidocaine and 0.25% bupivacaine, each with epinephrine (1:100,000 concentration ratio) was used. Pain control during the instillation of transperineal prostatic block and transurethral needle ablation was assessed using a 10-point linear analog pain scale and questionnaire. RESULTS: Median patient age was 65.5 years (range 47 to 79), with 21% of men in the eighth decade of life. Median American Urological Association symptom score was 25.0 (range 14 to 35), bother score was 20.0 (11 to 28), quality of life score was 4.0 (3 to 6) and peak urinary flow rate was 8.9 cc per second (3.5 to 15.7). Median sonographic prostate volume was 35.0 cc (range 17 to 129). Median volume of anesthetic agent used was 40.0 cc (range 30 to 60) per case (1.1 cc solution per 1 cc prostate tissue). No adverse events were encountered. Median pain score was 3.3 (range 1 to 6) during instillation of transperineal prostatic block and 1.0 (0 to 6) during transurethral needle ablation. Transperineal prostatic block proved highly effective and was a satisfactory method of anesthesia during transurethral needle ablation as judged by postoperative questionnaire. No sedation, narcotic or analgesia was required. All procedures were performed in the outpatient cystoscopy suite or office setting without support of an anesthesia team or conscious sedation monitoring. CONCLUSIONS: Transperineal prostatic block is a safe, convenient, effective and satisfactory method of minimally invasive anesthesia for transurethral needle ablation of the prostate in an outpatient office setting. Elderly patients and those at high surgical risk can be treated safely using this approach. Considerable cost saving is seen secondary to omission of charges related to anesthesia team support, recovery room facility and conscious sedation monitoring.
Asunto(s)
Hipertermia Inducida , Bloqueo Nervioso , Hiperplasia Prostática/terapia , Anciano , Estudios de Factibilidad , Humanos , Masculino , Persona de Mediana Edad , Agujas , Bloqueo Nervioso/métodos , Perineo , Estudios ProspectivosRESUMEN
We have examined the mechanisms of action of a broad spectrum of nitric oxide (NO) donors, including several S-nitrosothiols, sodium nitroprusside (SNP) and nitroglycerine (GTN), in relation to their relaxant activity of urethral smooth muscle. For all the compounds examined, NO release (in solution and in the presence of urethral tissue), relaxation responses, elevations in cGMP levels and the effect of thiol modulators were evaluated and compared with the effect of NO itself. Whilst all NO donors, except GTN, released NO in solution due to photolysis or chemical catalysis, this release was not correlated with their relaxant activity in sheep urethral preparations, which were furthermore not affected by the NO scavenger 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl 3-oxide (cPTIO; 0.3 mM). A substantial NO-generating activity was found for S-nitroso-L-cysteine (CysNO) and S-nitroso-N-acetyl-D,L-penicillamine (SNAP) in the presence of urethral cytosolic fractions, suggesting metabolic activation to NO in the cytosol of the target tissue. In contrast, NO generation from S-nitroso-N-acetyl-L-cysteine (N-ac-CysNO), S-nitrosoglutathione (GSNO) and SNP were reduced by the presence of urethral homogenate and/or subcellular fractions, suggesting direct NO transfer to tissue constituents. NO donors and NO gas induced dissimilar degrees of cGMP accumulation in urethral tissue, while they were essentially equipotent as urethral relaxants. Furthermore, 1H-[1,2,4] -oxadiazole-[4,3-a]-quinoxalin-1-one (ODQ; 10 microM) inhibited both relaxation and cGMP accumulations, but with different potency for the different compounds. Oxidation of sarcolemmal thiol groups with 5-5'-dithio-bis[2-nitrobenzoic acid] (DTNB; 0.5 mM) enhanced relaxations to GSNO, an effect that was reversed by dithiotreitol (DTT; 1 mM), suggesting a direct effect through nitrosylation/oxidation reactions at the cell membrane, while relaxations to NO and to all the other compounds were not affected by these treatments. Finally, photodegradation of SNP induced the formation of a stable intermediate that still evoked NO-cGMP-mediated relaxations. This indicates that the assumption that SNP is fully depleted of NO by exposure to light should be revised. It can be concluded that important differences exist in the mechanisms by which distinct NO donors relax urethral smooth muscle and they cannot be regarded simply as NO-releasing prodrugs.
Asunto(s)
Músculo Liso/efectos de los fármacos , Donantes de Óxido Nítrico/farmacología , Óxido Nítrico/farmacología , Uretra/efectos de los fármacos , Alquilación , Animales , Biotransformación , GMP Cíclico/fisiología , Femenino , Técnicas In Vitro , Luz , Relajación Muscular/efectos de los fármacos , Músculo Liso/fisiología , Óxido Nítrico/biosíntesis , Donantes de Óxido Nítrico/metabolismo , Donantes de Óxido Nítrico/farmacocinética , Donantes de Óxido Nítrico/efectos de la radiación , Nitroprusiato/farmacología , Nitroprusiato/efectos de la radiación , Ovinos , Compuestos de Sulfhidrilo/metabolismo , Compuestos de Sulfhidrilo/efectos de la radiación , Uretra/fisiología , Vasodilatadores/farmacologíaRESUMEN
1. The effects of endothelin-1 (ET-1) were studied in bovine oviductal arteries and compared to those of noradrenaline (NA) and high K+ (K+). The influence of endothelium, the receptor subtypes involved, and the mechanisms of Ca2+ mobilization were assessed. 2. ET-1 (0.1-300 nM) induced concentration-dependent contractions with a potency of 10(3) and 10(2) times higher than NA (0.1 microM-0.1 mM) and K+ (9.5-119 mM), respectively. Removal of endothelium or NG-nitro-L-arginine (L-NOARG, 0.1 mM) pretreatment did not affect responses to either ET-1 or K+, whereas the NA response was significantly increased. Indomethacin (1 microM) had no effect on either of these agonists. 3. The rank order of potency for the ET isopeptides was: ET-1 = ET-2 > ET-3. The ETA receptor-selective agonist, sarafotoxin 6c (S6c), had no effect. The ETA receptor-selective antagonist, BQ-123, showed a competitive antagonism on the ET-1 response (pA2 value of 6.58 +/- 0.01), whereas contractions to ET-3 were completely abolished by BQ-123 at 0.1 microM. 4. Concentration-response curves to both ET-1 and NA were shifted to the right and their maximum response reduced to approximately 56% and 65% of controls, respectively, under 30 min of incubation in Ca(2+)-free solution, whereas responses to K+ were almost abolished by this treatment. Contractions to both NA (30 microM) and ET-1 (30 nM) were maximally inhibited after 10 min of extracellular Ca2+ deprivation. 5. Contractions to ET-1 were more potently inhibited by nickel (Ni2+, 0.3 mM), whereas nifedipine (1 microM) and cadmium (Cd2+, 0.1 mM) induced only a slight effect. In contrast, opposite effects were found for both NA and K+. 6. Treatment with ryanodine (100 microM) and caffeine (10 mM) in Ca(2+)-free solution reduced the tension measured 5 min after NA (30 microM) and ET-1 (30 nM) addition, but the sustained response (tension at 25 min) remained unaffected. 7. Calphostin C (1 microM), a specific protein kinase C (PKC) inhibitor, reduced the maximum contractile response to ET-1 by about 50% without significantly affecting its pD2 value. 8. These results suggest that ET-1 acts in bovine oviductal arteries by directly activating a homogenous population of ETA receptors in smooth muscle, without endothelial modulation. Several Ca2+ activation mechanisms seem to be involved in the contractile action of the peptide, including: (1) extracellular Ca2+ entrance through Ni(2+)-sensitive and L-type Ca2+ channels; (2) intracellular Ca2+ release from a ryanodine-sensitive Ca2+ store; and (3) sensitization of the contractile machinery to Ca2+ via PKC.
Asunto(s)
Trompas Uterinas/irrigación sanguínea , Músculo Liso Vascular/efectos de los fármacos , Norepinefrina/farmacología , Potasio/farmacología , Receptores de Endotelina/fisiología , Animales , Cadmio/farmacología , Cafeína/farmacología , Calcio/metabolismo , Agonistas de los Canales de Calcio/farmacología , Bovinos , Antagonistas de los Receptores de Endotelina , Endotelina-1/farmacología , Endotelina-2/farmacología , Endotelina-3/farmacología , Endotelio Vascular/fisiología , Femenino , Técnicas In Vitro , Indometacina/farmacología , Contracción Muscular/efectos de los fármacos , Níquel/farmacología , Nifedipino/farmacología , Nitroarginina/farmacología , Péptidos Cíclicos/farmacología , Receptores de Endotelina/agonistas , Receptores de Endotelina/efectos de los fármacos , Receptores de Endotelina/metabolismo , Rianodina/farmacología , Venenos de Víboras/farmacologíaRESUMEN
The present in vitro study was designed to evaluate the effect of histamine on isolated rings of bovine oviductal artery and to characterize the histamine receptors involved in the histamine-induced response. Endothelial dependence of the response was also investigated. Cumulative addition of histamine and 2-pyridylethylamine (histamine H receptor agonist) induced a concentration-dependent relaxation in intact arterial segments precontracted with noradrenaline. The histamine H1 receptor antagonist mepyramine showed non-competitive antagonism in the histamine-induced concentration-response curve. However, when the response to histamine was evaluated in the presence of mepyramine and histamine H1 and H3 receptors were blocked, Schild analysis yielded a line with a slope of 1.10 and a pA2 value of 8.91, indicating simple competitive antagonism of mepyramine at histamine H1 receptor sites. The histamine H2 receptor agonist, dimaprit, caused marked dilatation only at high doses. Cimetidine, propranolol and mepyramine failed to inhibit this relaxant effect. In precontracted oviductal arteries, cimetidine did not modify the histamine-induced concentration-response curves. Combined treatment with histamine H1 and H2 receptor antagonists did not induce an additional displacement with respect to the isolated effect of mepyramine thus excluding activation of histamine H2 receptors. Histamine and (R)-alpha-methylhistamine, a selective histamine H3 receptor agonist, produced a moderate contractile effect on the resting tone of preparations. Pretreatment with the selective histamine H1 receptor antagonist decreased the (R)-alpha-methylhistamine response but increased the maximal relaxant effect and abolished the contractile effect of histamine, suggesting the presence of a limited population of contractile histamine H3 receptors. Removal of the endothelium or pretreatment with methylene blue produced a significant inhibition of the relaxant response to histamine. Remaining dilatation was practically abolished by mepyramine and also by indomethacin. The L-arginine analogue, N(omega)-nitro-L-arginine methyl ester (L-NAME) inhibited the effect of histamine and basal production of nitric oxide. L-Arginine, which on its own induced significant endothelium-dependent vasodilatation, reversed the effect of L-NAME on histamine relaxation. Indomethacin only caused a slight modification of the sensitivity of the vessels to histamine, suggesting that prostacyclin or other cyclo-oxygenase products did not make a significant contribution to the model. The absence of the endothelium did not modify the contractile effect of histamine. The results suggest that the relaxant response of isolated oviductal arteries to histamine is dependent on the functional integrity of the endothelium and is mainly mediated by histamine H1 receptors. These receptors may mask a minority presence of histamine H3 contractile receptors located on smooth muscle. The main relaxing factor released from the endothelium by mediation of histamine is nitric oxide, which may also exert an effect on vascular tone.
Asunto(s)
Endotelio Vascular/efectos de los fármacos , Trompas Uterinas/irrigación sanguínea , Histamina/farmacología , Receptores Histamínicos/metabolismo , Vasodilatadores/farmacología , Animales , Arterias/efectos de los fármacos , Arterias/metabolismo , Bovinos , Endotelio Vascular/metabolismo , Femenino , Técnicas In Vitro , Modelos Logísticos , Óxido Nítrico/farmacología , Receptores Histamínicos H1/efectos de los fármacos , Receptores Histamínicos H2/efectos de los fármacos , Receptores Histamínicos H3/efectos de los fármacosRESUMEN
1. Blood flow to the oviduct is implicated in the genesis and maintenance of oviductal fluid, in this way contributing to the creation of an adequate medium for ovum/embryo physiology. Therefore, factors controlling the tone of the vessels supplying the oviduct would be expected to affect its luminal environment. In addition, cyclic changes in oviductal blood flow have been suggested to have mechanical functions in the transport of the ovum/embryo. 2. The vascular supply to the oviduct has a prominent adrenergic vasomotor control. A dense adrenergic innervation, together with the presence of a predominant population of alpha(1)-adrenoceptors, provides a contractile regulatory mechanism of oviductal blood flow. No evidence is available on the presence of beta-adrenoceptors. The scanty cholinergic innervation of mammalian oviduct is mainly confined to the vessels, where acetylcholine (ACh) has a vasodilatory effect by releasing endothelium-derived relaxing factors. 3. The presence of nerves containing neuropeptides has been shown in the oviduct. Specifically, a high density of neuropeptide Y- and vasointestinal peptide-containing nerve fibers has been found in relation to blood vessels, but their role in the neutral control of the oviduct blood flow remains to be established. To date, it is not known whether or not oviductal blood vessels receive perivascular nitrergic nerves. 4. Relaxing and contracting factors derived from endothelium also seem to have a modulatory role on oviductal vascular tone. Neurotransmitters or autacoids, such as ACh and histamine, acting on endothelial receptors, release nitric oxide (NO), which relaxes oviductal arteries through guanylyl cyclase activation and accumulation of cyclic GMP. In addition, the release of an endothelium-derived hyperpolarizing factor (EDHF), distinct from NO, by ACh has been shown in oviductal arteries. It acts through the opening of low-conductance Ca(2+)-activated K+ channels leading to hyperpolarization and relaxation. Furthermore, potent and long-lasting contractions induced by the endothelium-derived contractile factor, endothelin (ET), points to its role in the long-term regulation of oviductal vascular tone. 5. A particularly high density of 5-hydroxytryptamine (5-HT) and histamine, present in mast cells clustered in the vicinity of blood vessels, has been described in the oviduct. It is known that histamine elicits a relaxation of oviductal arteries that is partially endothelium-dependent and mediated by the activation of H1-receptors. The implication of histamine in both the increase in blood flow and edema around ovulation, as well as the existence of a functional antagonism between histamine and 5-HT in the regulation of oviductal blood flow, await further investigation. 6. Other factors, such as relaxing and contracting cyclooxygenase-derived products, may also participate in the modulation of blood flow to the oviduct. 7. An overall endocrine regulation of the oviductal vascular supply exists, acting by both direct effects on smooth muscle and modulation of neural and autocrine factors. This control enables cyclic changes in blood flow to the oviduct that are tightly coupled to the reproductive functions of the tube.
Asunto(s)
Trompas Uterinas/irrigación sanguínea , Fibras Adrenérgicas/fisiología , Animales , Fibras Colinérgicas/fisiología , Endotelinas/fisiología , Trompas Uterinas/inervación , Trompas Uterinas/fisiología , Femenino , Histamina/fisiología , Humanos , Contracción Muscular/efectos de los fármacos , Músculo Liso Vascular/fisiología , Óxido Nítrico/fisiología , Serotonina/fisiologíaRESUMEN
We have investigated the wall tension characteristics and the role of endothelium on vascular tone, at rest and under K+ depolarization, in isolated rings from the pig capsular testicular artery. The active tension reached a maximum that was significantly lower in vessels without endothelium, whereas the passive tension and the Ca2+-dependent myogenic tone were not significantly affected by endothelium removal. Both NG-nitro-l-arginine (L-NOARG, 10(-4) M) and methylene blue (10(-5) M), increased the basal resting tension (BRT) in vessels with endothelium, while indomethacin (10(-6) M) decreased BRT in vessels both with and without endothelium. Either removal of endothelium or treatment with indomethacin (10(-6) M), quinacrine (10(-5) M) or ibuprofen (10(-5) M), significantly depressed the K+ concentration response curve, while dazoxiben (10(-5) M) and SQ 30,741 (10(-5) M) had no effect. L-NOARG (10(-6) M) potentiated the contractile response to K+ in vessels with endothelium, whereas L-NOARG (10(-4) M) was ineffective in vessels devoid of endothelium. These results suggest that a predominating NO release from endothelium, together with a cyclooxygenase-derived vasoconstrictor, modulate vascular tone at rest. In contrast, predominant endothelial release of a cyclooxygenase-derived contractile factor, but different from TXA2, PGH2 or superoxide anions, is induced by K+ depolarization and leads to vasoconstriction.
Asunto(s)
Endotelio Vascular/fisiología , Testículo/irrigación sanguínea , Sistema Vasomotor/fisiología , Animales , Arterias/fisiología , Dinoprost/farmacología , Relación Dosis-Respuesta a Droga , Inhibidores Enzimáticos/farmacología , Indometacina/farmacología , Masculino , Azul de Metileno/farmacología , Nitroarginina/farmacología , Concentración Osmolar , Potasio/farmacología , Vasoconstricción/efectos de los fármacosRESUMEN
1. To define further the role of nitric oxide (NO) in urinary tract function, we have measured the presence of nitric oxide synthase (NOS) activity, and its relationship with functional NO-mediated responses to electrical field stimulation (EFS) in the urethra, the detrusor and the ureter from sheep. NOS activity was assayed by the conversion of L-[14C]-arginine to L-[14C]-citrulline. Endogenous production of citrulline was confirmed by thin layer chromatography. 2. NOS enzymatic activity was detected in the cytosolic fraction from tissue homogenates with the following regional distribution (pmol citrulline mg-1 protein min-1): urethra (33 +/- 3.3), detrusor (13.1 +/- 1.1) and ureter (1.5 +/- 0.2). No activity was detected in the particulate fraction of any region. 3. NOS activity was dependent on Ca(2+)-calmodulin and required exogenously added NADPH and tetrahydrobyoptein (BH4) for maximal activity. Exclusion of calmodulin from the incubation mixture did not modify NOS activity, but it was significantly reduced in the presence of the calmodulin antagonist, calmidazolium, suggesting the presence of enough endogenous calmodulin to sustain the observed NOS activity. 4. NOS activity was inhibited to a greater extent by NG-nitro-L-arginine (L-NOARG) and its methyl ester (L-NAME) than by NG-monomethyl-L-arginine (L-NMMA), while 7-nitroindazole (7-NI) was a weak inhibitor and L-cannavine had no effect. 5. Citrulline formation could be inhibited by superoxide dismutase in an oxyhaemoglobin-sensitive manner, suggesting feedback inhibition of NOS by NO. 6. EFS induced prominent NO-mediated relaxations in the urethra while minor or no responses were observed in the detrusor and the ureter, respectively. Urethral relaxations to EFS were inhibited by NOS inhibitors with the rank order of potency: L-NOARG = L-NAME > 7-NI > L-NMMA. 7. In conclusion, we have demonstrated the presence of NO-synthesizing enzymatic activity in the sheep urinary tract which shows similar characteristics to the constitutive NOS isoform found in brain. We suggest that the enzymatic activity measured in the urethral muscle layer may account for the NO-mediated urethral relaxation during micturition whereas regulation of detrusor and ureteral motor function by NOS containing nerves is less likely.
Asunto(s)
Músculo Liso/enzimología , Óxido Nítrico Sintasa/metabolismo , Uréter/enzimología , Uretra/enzimología , Animales , Relación Dosis-Respuesta a Droga , Electroquímica , Femenino , Contracción Muscular/efectos de los fármacos , Relajación Muscular/efectos de los fármacos , Músculo Liso/efectos de los fármacos , NG-Nitroarginina Metil Éster/farmacología , Óxido Nítrico Sintasa/antagonistas & inhibidores , Nitroarginina/farmacología , Ovinos , Uréter/efectos de los fármacos , Uretra/efectos de los fármacos , omega-N-Metilarginina/farmacologíaRESUMEN
1. Mechanisms underlying the relaxant response to acetylcholine (ACh) were examined in bovine oviductal arteries (o.d. 300-500 microns and i.d. 150-300 microns) in vitro. Vascular rings were treated with indomethacin (10 microM) to prevent the effects of prostaglandins. 2. ACh elicited a concentration-related relaxation in ring segments precontracted with noradrenaline (NA), which was abolished by endothelium denudation. 3. The ACh-induced relaxation was attenuated but not abolished by NG-nitro-L-arginine (L-NOARG, 1 microM-1 mM), an inhibitor of nitric oxide (NO) formation. The inhibition caused by L-NOARG (10 microM) was reversed by addition of excess of L-arginine but not D-arginine (1 mM). 4. In high K+ (40-60 mM)-contracted rings, ACh was a much less effective vasodilator and its relaxant response was completely abolished by L-NOARG (100 microM). 5. In NA (10 microM)-contracted rings, ACh induced sustained and concentration-dependent increases in cyclic GMP, which were reduced below basal values by L-NOARG (100 microM), while potent relaxation persisted. Similar increases in cyclic GMP were evoked by ACh in high K+ (50 mM)-treated arteries and under these conditions, both cyclic GMP accumulation and relaxation were L-NOARG-sensitive. 6. S-nitroso-L-cysteine (NC), a proposed endogenous precursor of endothelial NO, also induced cyclic GMP accumulation in NA-contracted oviductal arteries. 7. Methylene blue (MB, 10 microM), a proposed inhibitor of soluble guanylate cyclase, inhibited both endothelium-dependent relaxation to ACh and endothelium-independent response to exogenous NO, whereas relaxation to NC remained unaffected. 8. The L-NOARG-resistant response to ACh was not affected by either ouabain (0.5 mM), glibenclamide (3 microM), tetraethylammonium (TEA, 1 mM) or charybdotoxin (50 nM), but was selectively blocked by apamin (0.1-1 microM). However, apamin did not inhibit either relaxation to ACh in high K(+)-contracted rings or endothelium-independent relaxation to either NO or NC. 9. Apamin and MB inhibited ACh-induced relaxation in an additive fashion, suggesting the involvement of two separate modulating mechanisms. 10. These results suggest that ACh relaxes bovine oviductal arteries by the release of two distinct endothelial factors: a NO-like substance derived from L-arginine, which induces cyclic GMP accumulation in smooth muscle, and another non-prostanoid factor acting by hyperpolarization mechanisms through alterations in apamin-sensitive K+ conductance.
Asunto(s)
Acetilcolina/farmacología , Endotelio Vascular/efectos de los fármacos , Trompas Uterinas/irrigación sanguínea , Óxido Nítrico/fisiología , Potasio/farmacología , S-Nitrosotioles , Animales , Apamina/farmacología , Arginina/análogos & derivados , Arginina/farmacología , Arterias/efectos de los fármacos , Arterias/fisiología , Bovinos , GMP Cíclico/metabolismo , Cisteína/análogos & derivados , Cisteína/farmacología , Endotelio Vascular/fisiología , Inhibidores Enzimáticos/farmacología , Femenino , Técnicas In Vitro , Azul de Metileno/farmacología , Relajación Muscular/efectos de los fármacos , Relajación Muscular/fisiología , Óxido Nítrico Sintasa/antagonistas & inhibidores , Nitroarginina , Ouabaína/farmacología , Potasio/metabolismo , Bloqueadores de los Canales de PotasioRESUMEN
1. In vitro experiments were designed to characterize postjunctional alpha-adrenoceptor subtypes in ring segments (1 mm length; outer diameter 300-500 microns) from arteries supplying the oviduct of the heifer. 2. Noradrenaline, adrenaline and phenylephrine evoked concentration-dependent contractile responses. The pD2 values were 5.67, 5.89 and 5.93, respectively. Medetomidine clonidine and B-HT 920 (2-amino-6-allyl-5,6,7,8-tetra-hydro-4H-(thiazo)-4,5-d-azepoine ) were ineffective. 3. The alpha-adrenoceptor selective antagonists, prazosin (1 nM-0.1 microM) and rauwolscine (0.1-10 microM) competitively antagonized the response to noradrenaline. The pA2 values were 9.38 and 6.83, respectively. 4. The dissociation constant (KD) for noradrenaline calculated by use of the irreversible antagonist, dibenamine, was 3.95 (2.09-5.81) microM. The occupancy-response relationship was non-linear. Half-maximal response to noradrenaline was obtained with 22% receptor occupancy while maximal response required 100% occupancy. 5. B-HT 920 evoked a biphasic contractile concentration-dependent response in preparations incubated in a physiological solution containing 20 mM K+, 0.1 microM prazosin and 1 microM propranolol. Rauwolscine 0.1 microM significantly (P less than 0.01) blocked the first component of the B-HT 920 concentration-response curve with an apparent pA2 value of 8.52 (7.86-9.18). 6. These results strongly suggest that alpha-adrenoceptors in oviductal arteries are mainly of the alpha 1 subtype, although a possible role for alpha 2-adrenoceptors cannot be excluded.
Asunto(s)
Trompas Uterinas/irrigación sanguínea , Receptores Adrenérgicos alfa/aislamiento & purificación , Acetilcolina/farmacología , Agonistas alfa-Adrenérgicos/farmacología , Antagonistas Adrenérgicos alfa/farmacología , Animales , Arterias/química , Arterias/efectos de los fármacos , Bovinos , Trompas Uterinas/metabolismo , Femenino , Hormonas Esteroides Gonadales/farmacología , Técnicas In Vitro , Norepinefrina/metabolismo , Norepinefrina/farmacología , Receptores Adrenérgicos alfa/efectos de los fármacos , Flujo Sanguíneo Regional/efectos de los fármacos , Flujo Sanguíneo Regional/fisiología , Sinapsis/metabolismoRESUMEN
A study was undertaken to determine the presence and distribution of alpha- and beta-adrenoceptors in the sheep bladder body and base. In the bladder body, noradrenaline and isoproterenol induced relaxation which was significantly inhibited by propranolol, pafenolol and butoxamine. In the presence of propranolol (10(-5) M), noradrenaline induced a small contraction, as well as phenylephrine, but B-HT 920 failed to cause any effect on the bladder body. In the bladder base, noradrenaline caused a contraction that was significantly inhibited by prazosin but not by yohimbine. Phenylephrine also induced a contractile response in this structure which was inhibited by prazosin. Isoproterenol caused a relaxation that was significantly inhibited by propranolol and pafenolol but not by butoxamine. Relaxation was mediated by both beta 1 and beta 2-adrenoceptors in the detrusor muscle and by beta 1-adrenoceptors in the bladder base. Alpha 1-adrenoceptors contributed to maintain the detrusor tone and contract the bladder base.
Asunto(s)
Músculo Liso/metabolismo , Receptores Adrenérgicos alfa/análisis , Receptores Adrenérgicos beta/análisis , Ovinos/metabolismo , Vejiga Urinaria/metabolismo , Antagonistas Adrenérgicos beta/farmacología , Animales , Butoxamina/farmacología , Isoproterenol/antagonistas & inhibidores , Isoproterenol/farmacología , Masculino , Contracción Muscular/efectos de los fármacos , Relajación Muscular/efectos de los fármacos , Músculo Liso/efectos de los fármacos , Norepinefrina/antagonistas & inhibidores , Norepinefrina/farmacología , Fenilefrina/farmacología , Prazosina/farmacología , Propanolaminas/farmacología , Propranolol/farmacología , Vejiga Urinaria/efectos de los fármacos , Yohimbina/farmacologíaRESUMEN
Two enzymeimmunoassays, homologous and heterologous, have been used for measuring progesterone in unextracted bovine milk using HRP as the enzyme label. Antibody raised by immunization of the rabbit against 11 alpha-hemisuccinate-BSA was used for the homologous system (EIA-11 alpha) and 7 alpha-carboxyethylthioether-BSA (EIA-7 alpha) for the heterologous. The progesterone derivatives used for the enzyme-hormone conjugates were 11 alpha-hemisuccinate and 6 beta-OH-hemisuccinate respectively. Milk progesterone in 60 samples measured by EIA-11 alpha and EIA-7 alpha were highly correlated (r = 0.93). Both systems were further compared with a conventional direct progesterone radioimmunoassay (RIA) in regular use for the same samples showing a good correlation. The sensitivity estimated was much higher in the EIA-7 alpha (0.5 pg/well) than in the EIA-11 alpha (32 pg/well).
Asunto(s)
Técnicas para Inmunoenzimas , Leche/química , Progesterona/análisis , Albúmina Sérica Bovina/inmunología , Animales , Bovinos , Femenino , RadioinmunoensayoRESUMEN
alpha and beta-adrenergic receptors in detrusor muscle and bladder base of horses were investigated by in vitro responses of smooth muscle strips to exogenous agonist and antagonist drugs. Noradrenaline, isoprenaline and salbutamol induced relaxation of detrusor muscle strips which was significantly inhibited by propranolol and butoxamine suggesting that the response is mediated by beta-2 adrenergic receptors. In the urinary bladder base noradrenaline, phenylephrine and B-HT 920 induced strong contractile effects. These contractile responses were inhibited by the alpha antagonist phenoxybenzamine, the alpha-1 selective antagonist prazosin and the alpha-2 selective antagonist yohimbine. The inhibitory action of prazosin was more potent than that observed with yohimbine suggesting that the response in the bladder base of horses is mediated predominantly by alpha-1 adrenergic receptors, although alpha-2 receptors also participate.
Asunto(s)
Sistema Nervioso Autónomo/fisiología , Caballos/fisiología , Receptores Adrenérgicos alfa/fisiología , Receptores Adrenérgicos beta/fisiología , Vejiga Urinaria/inervación , Agonistas alfa-Adrenérgicos/farmacología , Antagonistas Adrenérgicos alfa/farmacología , Agonistas Adrenérgicos beta/farmacología , Antagonistas Adrenérgicos beta/farmacología , Animales , Técnicas In Vitro , Músculo Liso/efectos de los fármacos , Receptores Adrenérgicos alfa/efectos de los fármacos , Receptores Adrenérgicos beta/efectos de los fármacos , Vejiga Urinaria/efectos de los fármacosRESUMEN
The presence of both alpha and beta adrenergic receptors in the caudal third ureter of the horse were studied in vitro under isometric conditions using adrenergic agonist and antagonist drugs. Isoprenaline and the beta 2- stimulating agent, salbutamol, elicited relaxation of the ureter smooth muscle strips. The responses were not affected by the beta 1- blocking agent, practolol, but were totally abolished by propranolol and the beta 2- blocking agent, butoxamine. The stimulation of alpha-adrenergic receptors with noradrenaline and phenylephrine evoked a contractile effect which was totally inhibited by phenoxybenzamine and the alpha 1- blocking agent, prazosin. It is concluded that in the horse ureter the alpha receptors are dominant and belong to alpha 1 subtype while the beta receptors are recessive and belong to beta 2- adrenoceptor subtype.
Asunto(s)
Receptores Adrenérgicos alfa/análisis , Receptores Adrenérgicos beta/análisis , Uréter/análisis , Animales , Caballos , Contracción Muscular , Relajación Muscular , Músculo Liso/análisisRESUMEN
The existence and subtypes of alpha- and beta-adrenoceptors in the female dog urethra were studied in vivo and in vitro by means of agonist and antagonist drugs. Noradrenaline, phenylephrine and B-HT 920, stimulants of alpha, alpha-1 and alpha-2 receptors respectively, caused an increase in the urethra tonicity. Thus indicating that the contractile activity is mediated by alpha-1 and alpha-2 adrenoceptors subtypes. On the other hand, the inhibitory urethral activity is under control of beta-adrenoceptors of beta-2 subtype, since the isoprenaline relaxing action is inhibited when beta-2 receptors are blocked, whilst this effect was not observed when beta-1 receptors were blocked. This fact was proved when beta-2 receptors were stimulated with salbutamol.
Asunto(s)
Receptores Adrenérgicos alfa/fisiología , Receptores Adrenérgicos beta/fisiología , Uretra/fisiología , Agonistas alfa-Adrenérgicos/farmacología , Antagonistas Adrenérgicos alfa/farmacología , Agonistas Adrenérgicos beta/farmacología , Antagonistas Adrenérgicos beta/farmacología , Animales , Perros , Femenino , Técnicas In Vitro , Contracción Muscular/efectos de los fármacos , Receptores Adrenérgicos alfa/efectos de los fármacos , Receptores Adrenérgicos beta/efectos de los fármacos , Uretra/efectos de los fármacosRESUMEN
The effects of verapamil, a calcium antagonist agent, were studied on smooth muscle preparations of the lower urinary tract of horses. Verapamil (2 X 10(-4) to 2 X 10(-8) M) relaxed the ureter, urethra and urinary bladder preparations contracted by potassium (127 mM), L-noradrenaline (2 X 10(-5) M), histamine (2 X 10(-5) M) and acetylcholine (2 X 10(-5) M). These results allow the conclusion that verapamil has a dose-dependent relaxing effect on smooth muscle of the lower urinary tract.