RESUMEN
The participation of endothelins (ETs) in a model of neutrophil-dependent lung injury induced by intrabronchial instillation of rabbit antibodies to ovalbumin followed by i.v. injection of the antigens (Arthus reaction) was investigated. Hemorrhagic lesions were evaluated by measuring the extravasations of hemoglobin in lung parenchyma. From 5 min to 24 h after the Arthus reaction (AR), endothelin (ir-ET) levels in bronchoalveolar lavage fluid (BALF) and in plasma were measured by radioimmunoassay. BALF levels of ir-ET were not different between control and AR animals for the first 90 min after the antigen challenge but increased from 2 to 24 h after induction of AR. ET levels in the plasma did not change from the respective controls over the same 24 h period. Increased ir-ET in BALF was not affected by pretreatment with L-NAME (30 mg/kg, i.v.). A PAF antagonist (BN52021; 5 and 10 mg/kg, i.v.) increased ET content in BALF and decreased the intensity of the AR. Thiorphan (2 mg/kg, i.v.) inhibited the AR-induced hemorrhagic lesions in lungs. An ET(A) receptor antagonist, BQ-123 (1 mg/kg, i.v.) potentiated, whereas the ET(B) antagonist, BQ-788 (1 mg/kg, i.v.) inhibited the lung hemorrhage. It is concluded that ETs are released during and play a role in the lung AR.
Asunto(s)
Reacción de Arthus/inmunología , Endotelinas/metabolismo , Hemorragia/inmunología , Enfermedades Pulmonares/inmunología , Neumonía/inmunología , Animales , Complejo Antígeno-Anticuerpo , Reacción de Arthus/sangre , Reacción de Arthus/etiología , Líquido del Lavado Bronquioalveolar/química , Diterpenos/farmacología , Antagonistas de los Receptores de la Endotelina A , Antagonistas de los Receptores de la Endotelina B , Endotelinas/análisis , Endotelinas/sangre , Fibrinolíticos/farmacología , Ginkgólidos , Hemoglobinas/análisis , Hemorragia/etiología , Hemorragia/metabolismo , Lactonas/farmacología , Enfermedades Pulmonares/etiología , Enfermedades Pulmonares/metabolismo , Masculino , Neutrófilos/inmunología , Oligopéptidos/farmacología , Ovalbúmina , Péptidos Cíclicos/farmacología , Piperidinas/farmacología , Neumonía/patología , Ratas , Ratas WistarRESUMEN
Endothelin-1 causes ET(A) receptor-mediated enhancement of capsaicin-induced nociception in mice. We have assessed if this hyperalgesic effect of endothelin-1 is also accompanied by other pro-inflammatory effects, namely nociception and oedema, and characterized the endothelin ET receptors involved. Intraplantar (i. pl.) hind-paw injection of endothelin-1 (0.3 - 30 pmol) induced graded nociceptive responses (accumulated licking time: vehicle, 20. 5+/-3.3 s; endothelin-1 at 30 pmol, 78.1+/-9.8 s), largely confined to the first 15 min. Endothelin-1 (1 - 10 pmol) potentiated ipsilateral capsaicin-induced (0.1 microgram, i.pl.; at 30 min) nociception (vehicle, 40.2+/-2.6 s; endothelin-1 at 10 pmol, 98.4+/-5.8 s, but 30 pmol was inactive), and caused oedema (increase in paw weight 5 min after capsaicin: vehicle, 46.3+/-2.3 mg; endothelin-1 at 30 pmol, 100.3+/-6.1 mg). Selective ET(B) receptor agonists sarafotoxin S6c (up to 30 pmol) and IRL 1620 (up to 100 pmol) were inactive, whereas endothelin-3 (up to 30 pmol) induced only modest oedema. ET(A) receptor antagonists BQ-123 (1 nmol, i.pl. ) or A-127722-5 (6 micromol kg(-1), i.v.) prevented all effects of endothelin-1 (10 pmol), but the ET(B) receptor antagonist BQ-788 (1 or 10 nmol, i.pl.) was ineffective. BQ-788 (10 nmol, i.pl.) unveiled hyperalgesic effects of 30 pmol endothelin-1 and endothelin-3. Sarafotoxin S6c (30 pmol, i.pl.) did not modify endothelin-1-induced (10 pmol) nociception or oedema, but abolished hyperalgesia. Thus, endothelin-1 triggers ET(A) receptor-mediated nociception, hyperalgesia and oedema in the mouse hind-paw. Simultaneous activation of ET(B) receptors by endothelin-1 or selective agonists can limit the hyperalgesic, but not the nociceptive or oedematogenic, effects of the peptide.
Asunto(s)
Edema/inducido químicamente , Endotelina-1/farmacología , Hiperalgesia/inducido químicamente , Nociceptores/efectos de los fármacos , Receptores de Endotelina/agonistas , Receptores de Endotelina/efectos de los fármacos , Animales , Atrasentán , Capsaicina , Edema/patología , Antagonistas de los Receptores de Endotelina , Endotelinas/farmacología , Masculino , Ratones , Oligopéptidos/farmacología , Fragmentos de Péptidos/farmacología , Péptidos Cíclicos/farmacología , Piperidinas/farmacología , Pirrolidinas/farmacología , Receptor de Endotelina A , Receptor de Endotelina B , Venenos de Víboras/farmacologíaRESUMEN
1. The influence of endothelin receptor antagonists on febrile responses to E. coli lipopolysaccharide (LPS), interleukin-1beta (IL-1beta), tumour necrosis factor-alpha (TNF-alpha) and endothelin-1 (ET-1) was assessed in conscious rats. 2. Intravenous (i.v.) LPS (5.0 microg kg(-1)) markedly increased rectal temperature to a peak of 1.30 degrees C over baseline at 2.5 h. Pretreatment with the mixed endothelin ET(A)/ET(B) receptor antagonist bosentan (10 mg kg(-1), i.v.) or the selective endothelin ET(B) receptor antagonist BQ-788 (N-cis-2,6-dimethylpiperidinocarbonyl-L-gamma-methylleucyl-D -1-methoxycarboyl-D-norleucine; 3 pmol, into a lateral cerebral ventricle-i.c.v.) reduced the peak response to LPS to 0.90 and 0.75 degrees C, respectively. The selective endothelin ET(A) receptor antagonist BQ-123 (cyclo[D-Trp-D-Asp-Pro-D-Val-Leu]; 3 pmol, i.c.v.) was ineffective. 3. Increases in temperature caused by IL-1beta (180 fmol, i.c.v.), TNF-alpha (14.4 pmol, i.c.v.) or IL-1beta (150 pmol kg(-1), i.v.) were unaffected by BQ-788 (3 pmol, i.c.v.). 4. Central injection of endothelin-1 (0.1 to 3 fmol, i.c.v.) caused slowly-developing and long-lasting increases in rectal temperature (starting 2 h after administration and peaking at 4-6 h between 0.90 and 1.15 degrees C) which were not clearly dose-dependent. The response to endothelin-1 (1 fmol, i.c.v.) was prevented by BQ-788, but not by BQ-123 (each at 3 pmol, i.c.v.). Intraperitoneal pretreatment with the cyclo-oxygenase inhibitor indomethacin (2 mg kg(-1)), which partially reduced LPS-induced fever, did not modify the hyperthermic response to endothelin-1 (3 fmol, i.c.v.). 5. Therefore, central endothelin(s) participates importantly in the development of LPS-induced fever, via activation of a prostanoid-independent endothelin ET(B) receptor-mediated mechanism possibly not situated downstream from IL-1beta or TNF-alpha in the fever cascade.
Asunto(s)
Fiebre/inducido químicamente , Lipopolisacáridos/farmacología , Receptores de Endotelina/fisiología , Animales , Antagonistas de los Receptores de Endotelina , Escherichia coli/química , Indometacina/farmacología , Inyecciones Intravenosas , Interleucina-1/farmacología , Masculino , Ratas , Ratas Wistar , Factor de Necrosis Tumoral alfa/farmacologíaRESUMEN
The influence of endothelin-1 on nociception induced by capsaicin was assessed in the mouse hindpaw. Local endothelin-1 injection (1 to 20 pmol/paw) 30 min prior to ipsilateral injection of capsaicin (0.1 microg/paw) increased, in a graded fashion, the time spent licking the injected paw. Maximal hyperalgesia was obtained with 10 pmol/paw of endothelin-1 (capsaicin-induced hindpaw licking time increased from 43 +/- 3 s to 114 +/- 7 s, n = 6), but no hyperalgesia was evident following 30 pmol/paw of endothelin-1. The selective endothelin ET(B) receptor agonists sarafotoxin S6c (< or = 30 pmol/paw) and IRL 1620 (i.e., Suc[Glu9,Ala11,15]endothelin-1-(10-21); < or = 100 pmol/paw) failed to induce hyperalgesia. Local treatment with BQ-123 (i.e., cyclo[DTrp-DAsp-Pro-DVal-Leu] 1 nmol/paw selective endothelin ET(A) receptor antagonist), 10 min before endothelin-1 (10 pmol/paw), fully blocked the hyperalgesic response, whereas similar treatment with the selective endothelin ET(B) receptor antagonist BQ-788 (i.e., N-cis-2,6-dimethylpiperidinocarbonyl-L-gamma-methylleucyl-D- 1-methoxy-carboyl-D-norleucine) was ineffective. Intravenous injection of bosentan (17 and 52 micromol/kg a non-peptidic mixed endothelin ET(A)/ET(B) receptor antagonist) or BMS 182874 (i.e., 5-[dimethylamino]-N-[3,4-dimethyl-5-isoxazolyl]-1-naphthalenesulph onamide; 10 and 30 micromol/kg; a non-peptidic selective endothelin ET(A) receptor antagonist), 1 h before endothelin-1, inhibited its hyperalgesic effect in a graded fashion and abolished the response at the higher doses. None of the antagonists modified nociception induced by capsaicin alone or the hyperalgesia induced by local injection of 5-hydroxytryptamine (5-HT; 2 nmol/paw, 30 min before capsaicin). Hyperalgesia induced by 5-HT was abolished by simultaneous injection of endothelin-1 or the endothelin ET(B) receptor agonist IRL 1620 (each at 30 pmol/paw). Therefore, local endothelin-1 exerts a dual influence in this model: at low doses it causes endothelin ET(A) receptor-mediated hyperalgesia (i.e., it potentiates capsaicin-induced nociception), whereas at higher doses it induces an anti-hyperalgesic effect against 5-HT which seems to be mediated via distinct endothelin ET (possibly ET(B)) receptors.
Asunto(s)
Analgesia , Endotelina-1/farmacología , Hiperalgesia/tratamiento farmacológico , Animales , Bosentán , Capsaicina , Compuestos de Dansilo/farmacología , Relación Dosis-Respuesta a Droga , Antagonistas de los Receptores de Endotelina , Endotelina-1/administración & dosificación , Endotelinas/farmacología , Miembro Posterior , Hiperalgesia/inducido químicamente , Masculino , Ratones , Oligopéptidos/farmacología , Fragmentos de Péptidos/farmacología , Péptidos/farmacología , Péptidos Cíclicos/farmacología , Piperidinas/farmacología , Receptor de Endotelina A , Receptor de Endotelina B , Receptores de Endotelina/agonistas , Serotonina/farmacología , Sulfonamidas/farmacología , Venenos de VíborasRESUMEN
Endothelin-1 (ET-1; 3-100 nM) caused graded tonic contractions and enhanced neurogenic contractions in rat field-stimulated seminal vesicle. At 100 nM, ET-1 increased nerve-mediated responses by 350 +/- 74 mg/100 mg wet tissue (almost 100% potentiation), whereas sarafotoxin S6c was ineffective. The potentiation of neurogenic responses by ET-1 was virtually abolished by the ETA receptor antagonist BQ-123 (1 microM; c. 95% inhibition) but was not modified by the ETB receptor antagonist BQ-788 (1 microM). Responses to field stimulation were inhibited by tetrodotoxin (0.1 microM; 100%), guanethidine (GTD; 5 microM, 75%), prazosin (PRA; 0.1 microM, 90%), desensitization of P2x purinoceptors with alpha,beta-methylene-ATP (mATP; 10 microM, 50%), or atropine (ATR; 0.1 microM, 40%). ET-1-induced potentiation of neurogenic contractions was not modified by prior incubation with indomethacin (5.6 microM), ATR, or PRA, but mATP and GTD reduced the effects of 100 nM ET-1 to 189 +/- 76 and 5 +/- 7 mg/100 mg wet tissue, respectively (n = 6-8). Therefore, ET-1 enhances nerve-mediated responses of this tissue by selectively potentiating the purinergic component of sympathetic neurotransmission. This action, which is independent of the eicosanoid-cycloxygenase pathway, is mediated via ETA receptors and, at least in part, by enhancement of motor responses to ATP.
Asunto(s)
Endotelina-1/farmacología , Receptores Purinérgicos/efectos de los fármacos , Vesículas Seminales/inervación , Sistema Nervioso Simpático/efectos de los fármacos , Transmisión Sináptica/efectos de los fármacos , Animales , Estimulación Eléctrica , Técnicas In Vitro , Masculino , Ratas , Ratas Wistar , Receptor de Endotelina B , Receptores de Endotelina/agonistas , Vesículas Seminales/efectos de los fármacos , Vasoconstrictores/farmacología , Venenos de Víboras/farmacologíaRESUMEN
This study assessed the possible local nociceptive and hyperalgesic properties of endothelin-1 (ET-1) in the rat knee-joint incapacitation test, in which animals are placed for 1 min/h on a revolving (3 rpm) metal cylinder and nociception is measured as the time the hindpaw of the injected limb was off the cylinder (i.e., paw elevation time, PET). Carrageenan (Cg; 150 micrograms/joint), E. coli LPS (1 microgram/joint), and ET-1 (120 or 240 pmol/joint) each increased PET persistently, unlike sarafotoxin S6c (120-240 pmol/joint) or PBS. ET-1 (15 and 30 pmol/joint, 30 min before) did not cause incapacitation per se but potentiated PET induced by Cg, increasing the area under the curve (AUC in arbitrary units, 0-6 h) from 105 +/- 9 to 165 +/- 10 and 169 +/- 25, respectively. Prior Cg injection (300 micrograms/joint, 72 h before) sensitized the joint to incapacitation triggered by restimulation with either Cg (300 micrograms/joint), LPS (1 microgram/joint), or ET-1 (30 pmol/joint). Treatment with bosentan (10 mg/kg i.v., 15 min before joint stimulation) did not affect PET values in naive animals to Cg or LPS, but significantly reduced the upregulated response evoked by restimulation with LPS (but not Cg), from 465 +/- 24 to 290 +/- 49 (AUC 0-12 h). Therefore, ET-1 triggers nociception and hyperalgesia in the naive knee joint of the rat, perhaps via ETA receptors. Although local endogenous ETs may not have a role in inflammatory nociception in the naive joint, they may participate in articular incapacitation induced by restimulation with LPS. This latter finding could be relevant to the etiology of pain associated with chronic arthritic diseases.
Asunto(s)
Artritis Experimental/patología , Endotelina-1/toxicidad , Miembro Posterior/patología , Hiperalgesia/inducido químicamente , Articulaciones/patología , Animales , Artritis Experimental/inducido químicamente , Bosentán , Carragenina , Antagonistas de los Receptores de Endotelina , Endotoxinas , Hiperalgesia/patología , Lipopolisacáridos , Masculino , Ratas , Ratas Wistar , Sulfonamidas/farmacología , Vasoconstrictores/farmacología , Venenos de Víboras/farmacologíaRESUMEN
The present study investigates the influence of endothelin (ET) related peptides (0.3-30 pmol/paw) on both phases of nociception and on edema induced by intraplantar injection of formalin (0.5% in 20 microL) in the mouse hind paw. The first phase of nociception (0-5 min after injection) was significantly potentiated by simultaneous injection of either ET-1 (10 or 30 pmol/paw) or ET-3 (10 pmol/paw), but not of the selective ET3 receptor agonist sarafotoxin S6c (SRTX-c; up to 30 pmol/paw). All three peptides potentiated the second phase (10-30 min after injection) of formalin-induced nociception (at 3-30, 1-30, and 10-30 pmol/paw for ET-1, ET-3, and SRTX-c, respectively), whereas only ET-1 (10 or 30 pmol/paw) effectively enhanced edema caused by formalin (30 min after injection). Histamine also potentiated all three responses triggered by formalin, but was 30- to 100-fold less potent than ET-1. Treatment with the mixed ETA/ETB receptor antagonist bosentan (10 mg/kg i.p., 1 h beforehand) did not influence nociceptive and edematogenic responses to formalin or their potentiation by histamine (3 nmol/paw), but did inhibit the potentiations induced by ET-1 (10 pmol/paw). Thus, ET-1 potentiates formalin-induced nociception and edema in the mouse. These actions are possibly mediated via ETB and ETA receptors, respectively, but their true identity and the mechanisms involved still remain to be fully elucidated.
Asunto(s)
Edema/inducido químicamente , Endotelina-1/toxicidad , Endotelina-2/toxicidad , Formaldehído/toxicidad , Nociceptores/efectos de los fármacos , Animales , Bosentán , Relación Dosis-Respuesta a Droga , Sinergismo Farmacológico , Antagonistas de los Receptores de Endotelina , Masculino , Ratones , Dimensión del Dolor , Receptor de Endotelina A , Receptor de Endotelina B , Sulfonamidas/farmacología , Venenos de Víboras/toxicidadRESUMEN
The receptors mediating guinea pig gall bladder (GPGB) contractions induced by endothelin-1 (ET-1) and related peptides were characterized using various ET receptor antagonists. As all ET-receptor agonists used, except sarafotoxin S6c (SRTX), failed to induce a clear-cut maximal response at the highest concentration tested (i.e. 100 nM), their potencies are expressed in terms of a CK50 (i.e. the concentration causing 50% of the response to 80 mM KCl). ET-1 (CK50 0.8 nM) was equipotent to ET-2 and SRTX (selective ET(B) receptor agonist), but more potent than ET-3 (5-fold) or IRL 1620 (selective ET(B) receptor agonist). BQ-123 (0.3 microM, peptidic ET(A) receptor antagonist) did not alter responses to ET-1, ET-3 or SRTX. BQ-788 (1 microM, peptidic ET(B) receptor antagonist) reduced the potency of ET-3 (9-fold at the CK50 level) and SRTX ( > 20-fold), but not ET-1. SRTX responses were unaffected by RES-701-1 (3 microM, peptidic ET(B) receptor antagonist). The combination BQ-123 (0.3 microM) plus BQ-788 (1 microM) did not modify responses to ET-1, inhibited SRTX responses similarly to BQ-788 alone and abolished ET-3 responses. Bosentan (1 microM, non-peptidic ET(A)/ET(B) receptor antagonist) reduced the potency of ET-1 (15-fold). ET-3 (9-fold) and SRTX (4-fold). In rat aorta, the antagonists blocked ET-1-induced contractions (BQ-123 and bosentan) or SRTX-induced endothelium-dependent relaxations (BQ-788, RES-701-1 and bosentan). Thus, the GPGB expresses both ET(A) and ET(B) receptors. As BQ-123 only blocked responses to ET-3 in the presence of BQ-788, there appears to be cross-talk between both receptor types. Also, the binding sites of ET-1 and ET-3 on the ET(A) receptor may not coincide entirely, as BQ-123, even in presence of BQ-788, did not affect ET-1-induced contractions.
Asunto(s)
Vesícula Biliar/metabolismo , Contracción Muscular , Receptores de Endotelina/metabolismo , Animales , Relación Dosis-Respuesta a Droga , Antagonistas de los Receptores de Endotelina , Femenino , Vesícula Biliar/efectos de los fármacos , Cobayas , Masculino , Contracción Muscular/efectos de los fármacos , Oligopéptidos/administración & dosificación , Oligopéptidos/farmacología , Péptidos/farmacología , Péptidos Cíclicos/administración & dosificación , Péptidos Cíclicos/farmacología , Piperidinas/administración & dosificación , Piperidinas/farmacología , Ratas , Receptor de Endotelina A , Receptor de Endotelina BRESUMEN
The endothelin receptors controlling sympathetic neurotransmission and the presence of endothelin-converting enzyme were investigated in the mouse vas deferens. Endothelin-1 or endothelin-3 (0.01-100 nM) enhanced contractions evoked by field stimulation, yielding EC50 (geometric mean and 95% confidence limits) of 0.7 nM (0.4-1.6) and 13.7 nM (10.2-14.1) and Emax (mean +/- S.E.M. increase in twitch tension, in mg/10 mg wet tissue) of 473 +/- 35 and 520 +/- 51, respectively. The selective endothelin ETB receptor agonists IRL 1620 (Suc-[Glu9,Ala11,15]endothelin-1) and sarafotoxin S6c were inactive up to 100 nM. Responses to endothelin-3 were progressively inhibited by the selective endothelin ETA receptor antagonist BQ-123 (cyclo[D-Trp-D-Asp-Pro-D-Val-Leu]) (10, 30 and 100 nM). At 100 nM, BQ-123 almost abolished the response to endothelin-3 (100 nM). In contrast, at 100, 300 nM and 1 microM, BQ-123 shifted the curve to endothelin-1 to the right only 2-, 5- and 6-fold, respectively. The selective endothelin ETB receptor antagonist BQ-788 (N-cis-2,6-dimethylpiperidinocarbonyl-L-gamma-methyl-leucyl-D-1-++ +methoxycarbonyltryptophanyl-D-norleucine) (100 nM) did not modify responses to endothelin-1 or endothelin-3 (0.01-100 nM). Big-endothelin-1 (0.3-30 nM) was 10-fold less potent than endothelin-1 in increasing neurogenic responses (EC50 6.8 nM, 4.7-9.6; Emax 457 +/- 37 mg/10 mg wet tissue). Preincubation with phosphoramidon (100 microM) reduced responses to big-endothelin-1, but not endothelin-1.(ABSTRACT TRUNCATED AT 250 WORDS)
Asunto(s)
Ácido Aspártico Endopeptidasas/metabolismo , Receptores de Endotelina/fisiología , Conducto Deferente/fisiología , Animales , Estimulación Eléctrica , Enzimas Convertidoras de Endotelina , Endotelinas/farmacología , Masculino , Metaloendopeptidasas , Ratones , Contracción Muscular , Oligopéptidos/farmacología , Péptidos Cíclicos/farmacología , Piperidinas/farmacología , Receptores de Endotelina/efectos de los fármacos , Conducto Deferente/efectos de los fármacos , Conducto Deferente/enzimologíaAsunto(s)
Fenómenos Fisiológicos del Sistema Digestivo , Endotelinas/farmacología , Endotelinas/fisiología , Músculo Liso/fisiología , Fenómenos Fisiológicos Respiratorios , Sistema Urogenital/fisiología , Animales , Sistema Digestivo/efectos de los fármacos , Endotelinas/biosíntesis , Femenino , Humanos , Masculino , Músculo Liso/efectos de los fármacos , Músculo Liso/metabolismo , Receptores de Endotelina/fisiología , Sistema Respiratorio/efectos de los fármacos , Transducción de Señal/fisiología , Sistema Urogenital/efectos de los fármacosRESUMEN
This study investigated the influence of the selective endothelin (ET) ETA receptor antagonists BQ-123 and FR 139317 on paw edema induced by ovalbumin (OVA) injection (3 micrograms/paw) to OVA-sensitized mice [50 micrograms in 5 mg of Al(OH)3, s.c., 14 days earlier]. Injections of BQ-123 (1.5, 15, and 150 pmol/paw, 15 min earlier) reduced OVA-induced edema from 59.6 +/- 4.0 to 48.3 +/- 5.4, 44.6 +/- 3.8, and 34 +/- 2.0 microliters, respectively (p < 0.05; n = 6). Like BQ-123, FR 139317 (7.5, 75, and 750 pmol/paw) also inhibited OVA-induced edema in a graded fashion but was less potent. In contrast, BQ-123 (150 pmol/paw) failed to affect paw edema induced in nonsensitized mice by histamine (100 micrograms/paw), serotonin (100 micrograms/paw), or zymosan (500 micrograms/paw), but significantly reduced edema induced by carrageenan (300 micrograms/paw) by 30% (p < 0.05). These results strongly suggest that endogenous ETs, acting through ETA receptors, play an important proinflammatory role in the allergic reaction to OVA.
Asunto(s)
Azepinas/uso terapéutico , Edema/prevención & control , Antagonistas de los Receptores de Endotelina , Indoles/uso terapéutico , Péptidos Cíclicos/uso terapéutico , Animales , Edema/etiología , Endotelinas/fisiología , Masculino , Ratones , Ovalbúmina/inmunología , Receptor de Endotelina ARESUMEN
Endothelin-1 (ET-1; 0.3-100 nM) induced graded tonic contractions in rat isolated seminal vesicle, with an EC50 of 7.2 nM and an Emax of 0.24 +/- 0.03 g/100 mg wet tissue. In contrast, norepinephrine (NE) and acetylcholine (ACh) caused short-lasting phasic contractions, yielding EC50s of 8.0 and 30.3 microM and Emaxs of 1.99 +/- 0.21 and 2.16 +/- 0.31, respectively. ET-3 and sarafotoxin S6c were 10- to 30-fold less potent than ET-1. Contractions to ET-1 (1-100 nM) were markedly inhibited by the selective ETA receptor antagonist BQ-123 (300 nM). ET-1 also potentiated, in graded fashion, contractions induced by ATP (1 mM; 30 nM of ET-1 caused a 10-fold potentiation) but not by NE (3 microM) or ACh (10 microM). Indomethacin (5.6 microM) reduced ET-1-induced contractions and abolished the potentiation of responses to ATP. Big ET-1 also contracted the preparation, being 10- to 15-fold less potent than ET-1. Therefore ET-1 causes modest tonic contractions of the rat seminal vesicle via stimulation of ETA receptors and selectively potentiates motor responses to ATP. Eicosanoids of the cycloxygenase pathway are involved in both effects.
Asunto(s)
Adenosina Trifosfato/farmacología , Endotelinas/farmacología , Vesículas Seminales/efectos de los fármacos , Animales , Indometacina/farmacología , Masculino , Contracción Muscular/efectos de los fármacos , Ratas , Ratas Wistar , Vesículas Seminales/fisiología , Venenos de Víboras/farmacologíaRESUMEN
The presence of a phosphoramidon-sensitive endothelin-1-converting enzyme was investigated in the rat isolated uterus. Endothelin-1 and its precursor, big-endothelin-1, increased the rate of spontaneous contractions and caused tonic contractions. Responses to big-endothelin-1 had a slower start than those to endothelin-1. The tonic contraction induced by big-endothelin-1 (10 nM) was nearly abolished by phosphoramidon (100 microM), but the response to an equieffective concentration of endothelin-1 (3 nM) was not affected. Big-endothelin-1 (EC50 6.7 nM) was only 7-fold less potent than endothelin-1 (EC50 0.9 nM), whereas endothelin-3 was much less potent (EC50 > 100 nM). The endothelin ETA receptor antagonist, BQ-123 (40, 150 and 600 nM), induced graded rightward shifts of the concentration-response curve for endothelin-1. Schild analysis yielded a straight line with a slope not different from unity, and a pA2 value of 7.76. At 100 nM, BQ-123 specifically blocked responses to both endothelin-1 (3 nM) and big-endothelin-1 (10 nM), without modifying those to oxytocin (5 nM), acetylcholine (3 microM) or bradykinin (0.5 nM). Our results suggest the presence of phosphoramidon-sensitive endothelin-converting enzyme and demonstrate the occurrence of functional endothelin ETA receptors in the rat uterus.
Asunto(s)
Endotelinas/farmacología , Glicopéptidos/farmacología , Músculo Liso/efectos de los fármacos , Precursores de Proteínas/farmacología , Receptores de Endotelina/metabolismo , Útero/efectos de los fármacos , Secuencia de Aminoácidos , Animales , Ácido Aspártico Endopeptidasas/metabolismo , Relación Dosis-Respuesta a Droga , Antagonistas de los Receptores de Endotelina , Endotelina-1 , Enzimas Convertidoras de Endotelina , Endotelinas/metabolismo , Femenino , Técnicas In Vitro , Metaloendopeptidasas , Datos de Secuencia Molecular , Contracción Muscular/efectos de los fármacos , Péptidos Cíclicos/farmacología , Precursores de Proteínas/metabolismo , Ratas , Ratas Wistar , Útero/metabolismoRESUMEN
Like endothelin-1 (ET-1), its immediate human precursor big ET-1 (1-100 nM) increased the rate of spontaneous phasic contractions and caused graded tonic contractions of isolated rat uterus strips. The tonic contraction to big ET-1 (10 nM) was markedly blocked by phosphoramidon (100 microM), which did not modify the response to an equipotent concentration of ET-1 (3 nM). Responses to big-ET-1 (30 nM) were abolished in calcium-free medium, but those to ET-1 (10 nM) were only reduced by this condition. The EC50 of big ET-1 for inducing tonic contraction was only sevenfold greater than that of ET-1, and both peptides produced a maximal response similar to that evoked by KCl 80 mM. ET-3 was much less potent. The selective ETA receptor antagonist BQ-123 (40-600 nM) caused graded rightward shifts of the ET-1 curve without affecting the maximal response, yielding a Schild plot with a slope not different from unity and a pA2 value of 7.76. BQ-123 (100 nM) did not affect contractions induced by oxytocin (5 nM), acetylcholine (3 microM), or bradykinin (0.3 nM), but inhibited responses to both big ET-1 and ET-1. Therefore, the rat uterus contains a phosphoramidon-sensitive, calcium-dependent endothelin-converting enzyme that readily converts big ET-1 into ET-1, which then contracts the myometrium via activation of ETA receptors.