RESUMO
BACKGROUND: Sickle cell disease patients display priapism that may progress to erectile dysfunction. However, little is known about the pathophysiological alterations of corpus cavernosum in sickle cell disease. OBJECTIVE: Thus, this study aimed to evaluate the functional and molecular alterations of sympathetic machinery and nitric oxide-cyclic guanosine monophosphate signaling pathway in Townes transgenic sickle cell disease mice. METHODS: Concentration-response curves to contractile (phenylephrine) and relaxant agents (acetylcholine and sodium nitroprusside) were obtained in corpus cavernosum strips from sickle and C57BL/6 (control) mice. Neurogenic contractions and nitrergic relaxations were obtained using electrical-field stimulation. Measurements of endothelial nitric oxide synthase (eNOS), neuronal nitric oxide synthase (nNOS), phosphodiesterase-5 (PDE5) and α1A-, α1B- and α1D-adrenoceptor mRNA expressions and reactive-oxygen species were performed. Tyrosine hydroxylase phosphorylated at Ser-31 and total tyrosine hydroxylase protein expressions in cavernosal tissues were also measured. RESULTS: The neurogenic contractions were higher in the sickle cell disease group, in association with elevated tyrosine hydroxylase phosphorylated at Ser-31 and total tyrosine hydroxylase protein expression, as well as increased tyrosine hydroxylase mRNA expression. Likewise, phenylephrine-induced contractions were greater in the sickle mice, whereas α1A-, α1B- and α1D-adrenoceptor mRNA expression remained unchanged. Cavernosal relaxations to acetylcholine, sodium nitroprusside and EFS were higher in sickle mice, accompanied by decreased eNOS and nNOS, along with lower PDE5 mRNA expression. An increase of about 40% in reactive-oxygen species generation in corpus cavernosum from sickle mice was also detected. CONCLUSION: Our study shows that decreased nitric oxide bioavailability in erectile tissue due to increased oxidative stress leads to both sympathetic hyperactivity and dysregulation of nitric oxide signaling in corpus cavernosum from Townes sickle mice.
Assuntos
Anemia Falciforme/fisiopatologia , Estresse Oxidativo , Pênis/fisiopatologia , Sistema Nervoso Simpático/fisiopatologia , Tirosina 3-Mono-Oxigenase/metabolismo , Acetilcolina/farmacologia , Anemia Falciforme/genética , Anemia Falciforme/metabolismo , Animais , Western Blotting , Nucleotídeo Cíclico Fosfodiesterase do Tipo 5/genética , Nucleotídeo Cíclico Fosfodiesterase do Tipo 5/metabolismo , Relação Dose-Resposta a Droga , Estimulação Elétrica , Expressão Gênica/efeitos dos fármacos , Técnicas In Vitro , Masculino , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Óxido Nítrico Sintase Tipo I/genética , Óxido Nítrico Sintase Tipo I/metabolismo , Óxido Nítrico Sintase Tipo III/genética , Óxido Nítrico Sintase Tipo III/metabolismo , Nitroprussiato/farmacologia , Pênis/efeitos dos fármacos , Pênis/inervação , Fosforilação/efeitos dos fármacos , Espécies Reativas de Oxigênio/metabolismo , Receptores Adrenérgicos/genética , Receptores Adrenérgicos/metabolismo , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Tirosina 3-Mono-Oxigenase/genética , Vasodilatadores/farmacologiaRESUMO
The nitric oxide-cGMP signaling pathway modulates the ejaculatory functions. The nitric oxide (NO)-independent soluble guanylate cyclase haem-dependent stimulator BAY 41-2272 potently relaxes different types of smooth muscles. However, no study investigated its effects in vas deferens smooth muscle. Therefore, we designed experiments to evaluate the in vitro relaxing responses of vas deferens to BAY 41-2272. The effects of prolonged oral intake with BAY 41-2272 in vas deferens contractions of rats treated chronically with the NO synthase inhibitor N(ω)-nitro-L-arginine methyl ester (L-NAME) were also investigated. BAY 41-2272 (0.001-100 µM) produced concentration-dependent relaxations in the prostatic and epididymal portions of vas deferens, an effect markedly reduced by the soluble guanylate cyclase inhibitor ODQ (100 µM). BAY 41-2272 significantly increased cGMP levels that were fully prevented by ODQ. In separate protocols, rats received L-NAME (20mg/rat/day) concomitantly with BAY 41-2272 (10mg/kg/day, 4 weeks), after which vas deferens contractions to electrical-field stimulation and noradrenaline were achieved. Electrical-field stimulation (1-32 Hz) evoked frequency-dependent contractions that were significantly enhanced in L-NAME-treated rats. Co-treatment with BAY 41-2272 fully reversed the increased contractile responses in L-NAME group. Noradrenaline (0.01-100 µM)-induced contractions were also greater in L-NAME-treated rats, and that was normalized by BAY 41-2272. In conclusion, BAY 41-2272 potently relaxes in vitro rat vas deferens smooth muscle and elevates the cGMP levels in an ODQ-sensitive manner. Moreover, prolonged oral intake with BAY 41-2272 restores the enhanced contractile vas deferens activity in rats treated with L-NAME. NO-independent soluble guanylate cyclase stimulators may be an alternative treatment for premature ejaculation.
Assuntos
Músculo Liso/efeitos dos fármacos , Músculo Liso/fisiologia , Pirazóis/farmacologia , Piridinas/farmacologia , Receptores Citoplasmáticos e Nucleares/agonistas , Ducto Deferente/efeitos dos fármacos , Ducto Deferente/fisiologia , Animais , GMP Cíclico/biossíntese , Estimulação Elétrica , Guanilato Ciclase , Técnicas In Vitro , Masculino , Contração Muscular/efeitos dos fármacos , Músculo Liso/metabolismo , Óxido Nítrico/metabolismo , Norepinefrina/farmacologia , Ratos , Ratos Wistar , Guanilil Ciclase Solúvel , Fatores de Tempo , Ducto Deferente/metabolismoRESUMO
OBJECTIVE: ⢠To investigate the potential beneficial effects of 4-week oral treatment with 5-cyclopropyl-2-[1-(2-fluoro-benzyl)-1Hpyrazolo[3,4-b]pyridin-3-yl]-pyrimidin-4-ylamine (BAY 41-2272), a nitric oxide (NO)-independent soluble guanylate cyclase activator, on impaired rat corpus cavernosum relaxations in NO-deficient rats. MATERIAL AND METHODS: ⢠Male Wistar rats were divided into four groups: Control, N (G)-nitro-L- arginine methyl ester (L-NAME; 20 mg/rat/day), BAY 41-2272 (20 mg/kg/day) and L-NAME + BAY 41-2272. ⢠Rats were treated with L-NAME concomitantly with BAY 41-2272 for 4 weeks. ⢠Concentration-response curves to acetylcholine (ACh) and sodium nitroprusside (SNP), along with the nitrergic relaxations (1-32 Hz) were obtained in rat corpus cavernosum (RaCC). ⢠The RaCC contractile responses to the α1 -adrenoceptor agonist phenylephrine (PE) were obtained. RESULTS: ⢠Acetylcholine (0.01-1000 µmol/L) produced concentration-dependent relaxing responses in RaCC that were significantly enhanced (P < 0.05) in BAY 41-2272-treated rats. ⢠The ACh-induced relaxations were largely reduced in L-NAME-treated rats, and co-treatment with BAY 41-2272 failed to significantly modify these impaired relaxations. ⢠The SNP-induced relaxations were modified neither by L-NAME nor by co-treatment with BAY 41-2272. ⢠The nitrergic relaxations were significantly amplified in BAY 41-2272-treated rats (at 16 and 32 Hz). A significant reduction in the nitrergic relaxations was observed in L-NAME-treated rats, an effect largely restored by co-treatment with BAY 41-2272. ⢠The contractile RaCC responses produced by PE (0.001-100 µmol/L) were significantly higher (P < 0.05) in L-NAME-treated rats, and co-treatment of L-NAME with BAY 41-2272 nearly restored these enhanced contractile responses. CONCLUSION: ⢠Four-week therapy with BAY 41-2272 prevents the impaired corpus cavernosum relaxations of rats treated chronically with L-NAME, indicating that accumulation of cyclic guanosine monophosphate into erectile tissue counteracts the NO deficiency.
Assuntos
GMP Cíclico/metabolismo , Disfunção Erétil/tratamento farmacológico , Relaxantes Musculares Centrais/farmacologia , Óxido Nítrico/deficiência , Ereção Peniana/efeitos dos fármacos , Pirazóis/farmacologia , Piridinas/farmacologia , Animais , Inibidores Enzimáticos/uso terapêutico , Disfunção Erétil/fisiopatologia , Guanilato Ciclase/metabolismo , Masculino , NG-Nitroarginina Metil Éster/uso terapêutico , Ereção Peniana/fisiologia , Ratos , Ratos WistarRESUMO
AIMS: The effect of exercise training (ET) on vascular responsiveness in diabetes mellitus has been largely well studied. However, limited studies have investigated the effects of ET on functional responses of the corpus cavernosum (CC) in diabetic animals. Therefore, the aim of this study was to investigate whether prior ET prevents the impairment of erectile function in streptozotocin-induced diabetic rats. MAIN METHODS: Rats were exercised for four weeks prior to the induction of diabetes, and then again for another 4 weeks thereafter. Concentration-response curves to acetylcholine, sodium nitroprusside, Y-27632, BAY 412272 and phenylephrine (PE) were obtained in CC. The excitatory and inhibitory effects of electrical-field stimulation were also evaluated. KEY FINDINGS: Plasma SOD levels were markedly decreased in the sedentary diabetic group (D-SD) as compared to control sedentary animals (C-SD), approximately 53% (P<0.05) and this reduction was restored in trained diabetic animals. Physical training restored the impairment of endothelium-dependent and -independent relaxation responses seen in the D-SD group. The potency values for Y-27632 in the CC were significantly reduced in the D-SD group, which was reversed by physical training. The impairment of electrical-field stimulation (EFS)-induced relaxation seen in the D-SD group was restored by physical training. On the other hand, both EFS-induced contractions and concentration-response curves to PE in cavernosal strips were not modified by either diabetes or physical training. SIGNIFICANCE: Practice of regular physical exercise may be an important approach in preventing erectile dysfunction associated with diabetes mellitus by re-establishment of the balance between NO production and its inactivation.
Assuntos
Diabetes Mellitus Experimental , Disfunção Erétil/complicações , Contração Muscular/fisiologia , Músculo Liso/fisiologia , Condicionamento Físico Animal/fisiologia , Animais , Células Cultivadas , Diabetes Mellitus Experimental/complicações , Disfunção Erétil/prevenção & controle , Masculino , Ereção Peniana/fisiologia , RatosRESUMO
OBJECTIVE: To investigate the effects of chronic ethanol consumption and diabetes on nitric oxide (NO)-mediated relaxation of cavernosal smooth muscle (CSM). MATERIAL AND METHODS: Male Wistar rats were divided into four groups: control, isocaloric, diabetic and ethanol-diabetic. The CSMs were mounted in organ chambers for measurement of isometric tension. Contraction of the strips was induced by electrical field stimulation (EFS, 1-32 Hz) and phenylephrine. We also evaluated the effect of ethanol consumption on the relaxation induced by acetylcholine (ACh; 0.01-1000 micromol/L), sodium nitroprusside (SNP, 0.01-1000 micromol/L) or EFS (1-32 Hz) in strips pre-contracted with phenylephrine (10 micromol/L). Immunoexpression of endothelial NO synthase (eNOS) and inducible NOS (iNOS) was also accessed. RESULTS: The endothelium-dependent relaxation induced by ACh was decreased in CSM from ethanol-diabetic rats when compared with the controls, with a mean (sem) of 21 (4) vs 37 (2)%. Similarly, the potency and maximal responses induced by SNP were reduced in the ethanol-diabetic [3.97 (0.38) and 85 (1)%, respectively] and diabetic groups [3.78 (0.56) and 81 (2)%, respectively] when compared with the controls [5.3 (0.22) and 90 (3)%, respectively] and isocaloric [5.3 (0.19) and 92 (1)%, respectively] groups. Noradrenergic nerve-mediated contractions of CSM in response to EFS were increased in rats from ethanol-diabetic and diabetic groups when compared with the control and isocaloric groups. Conversely, there were no differences in EFS-induced relaxation among the groups. The immunostaining assays showed overexpression of eNOS and iNOS in the CSM from diabetic and ethanol-diabetic rats when compared with the control and isocaloric rats. CONCLUSION: There was an impairment of relaxation of CSM from ethanol-diabetic and diabetic rats that involved a decrease in the NO-cyclic guanosine monophosphate signalling pathway by endothelium-dependent mechanisms accompanied by a change in the CSM contractile sensitivity.
Assuntos
Alcoolismo/complicações , Complicações do Diabetes/complicações , Disfunção Erétil/etiologia , Pênis/efeitos dos fármacos , Animais , Imuno-Histoquímica , Masculino , Contração Muscular/efeitos dos fármacos , Músculo Liso/efeitos dos fármacos , Nitroprussiato/farmacologia , Fenilefrina/farmacologia , Ratos , Ratos Wistar , Vasoconstritores/farmacologia , Vasodilatadores/farmacologiaRESUMO
OBJECTIVES: To test the hypothesis that glyco protein 91phox (gp91(phox)) subunit of nicotinamide adenine dinucleotide phosphate [NAD(P)H] oxidase is a fundamental target for physical activity to ameliorate erectile dysfunction (ED). Vascular risk factors are reported to contribute to ED. Regular physical exercise prevents cardiovascular diseases by increasing nitric oxide (NO) production and/or decreasing NO inactivation. METHODS: Male Wistar rats received the NO synthesis inhibitor N(omega)-nitro-l-arginine methyl ester (l-NAME) for 4 weeks, after which animals were submitted to a run training program for another 4 weeks. Erectile functions were evaluated by in vitro cavernosal relaxations and intracavernous pressure measurements. Expressions of gp91(phox) subunit and neuronal nitric oxidase synthase in erectile tissue, as well as superoxide dismutase activity and nitrite/nitrate (NO(x)) levels were determined. RESULTS: The in vitro acetylcholine- and electrical field stimulation-induced cavernosal relaxations, as well as the increases in intracavernous pressure were markedly reduced in sedentary rats treated with l-NAME. Run training significantly restored the impaired cavernosal relaxations. No alterations in the neuronal nitric oxidase synthase protein expression (and its variant penile neuronal nitric oxidase synthase) were detected. A reduction of NO(x) levels and superoxide dismutase activity was observed in l-NAME-treated animals, which was significantly reversed by physical training. Gene expression of subunit gp91(phox) was enhanced by approximately 2-fold in erectile tissue of l-NAME-treated rats, and that was restored to basal levels by run training. CONCLUSIONS: Our study shows that ED seen after long-term l-NAME treatment is associated with gp91(phox) subunit upregulation and decreased NO bioavailability. Exercise training reverses the increased oxidative stress in NO-deficient rats, ameliorating the ED.
Assuntos
Disfunção Erétil/enzimologia , Disfunção Erétil/terapia , Glicoproteínas de Membrana/fisiologia , NADPH Oxidases/fisiologia , Óxido Nítrico/antagonistas & inibidores , Condicionamento Físico Animal , Regulação para Cima , Animais , Disfunção Erétil/etiologia , Masculino , NADPH Oxidase 2 , Ratos , Ratos Wistar , Fatores de TempoRESUMO
OBJECTIVES: To investigate the effects of chronic ethanol consumption on nitric oxide (NO)-mediated relaxation in rat cavernosal smooth muscle (CSM). METHODS: Male wistar rats were divided into 2 groups: control and ethanol. CSM obtained from both groups were mounted in organ chambers for measurement of isometric tension. Contraction of the strips was induced by electrical field stimulation (EFS, 1-32 Hertz) and phenylephrine. We also evaluated the effect of ethanol consumption on the relaxation induced by acetylcholine (0.01-1000 micromol L(-1)), sodium nitroprusside (SNP, 0.01-1000 micromol L(-1)), or EFS (1-32 Hz) in strips precontracted with phenylephrine (10 micromol L(-1)). Blood ethanol, serum testosterone levels, and basal nitrate generation were determined. Immunoexpression of endothelial NO synthase (eNOS) and inducible NO synthase (iNOS) was also accessed. RESULTS: Ethanol intake for 4 weeks significantly increased noradrenergic nerve-mediated contractions of CSM in response to EFS. The endothelium-dependent relaxation induced by acetylcholine decreased after the ethanol treatment. Ethanol consumption decreased serum testosterone levels but did not affect the nitrate levels on rat CSM. The mRNA and protein levels for eNOS and iNOS receptors were increased in CSM from ethanol-treated rats. CONCLUSIONS: Ethanol consumption reduces endothelium-dependent relaxation induced by acetylcholine, but does not affect SNP or EFS-induced relaxation, suggesting that ethanol disrupts the endothelial function. Despite the overexpression of eNOS and iNOS in ethanol-treated rats, the impaired relaxation induced by acetylcholine may suggest that chronic ethanol consumption induces endothelial dysfunction.
Assuntos
Alcoolismo/fisiopatologia , Músculo Liso/fisiopatologia , Pênis/fisiopatologia , Animais , Masculino , Óxido Nítrico/fisiologia , Ratos , Ratos WistarRESUMO
OBJECTIVES: To compare the direct relaxant activity of sildenafil, vardenafil, and tadalafil in the human corpus cavernosum (HCC) and to investigate their modulatory effects on nitric oxide (NO)-mediated responses. Phosphodiesterase (PDE)-5 inhibitors cause cavernosal smooth muscle relaxation and penile erection. METHODS: HCC strips were mounted in 10-mL organ baths containing Krebs solution and connected to force-displacement transducers. The changes in isometric force were recorded using the Powerlab 400 data acquisition system. Corporeal smooth muscle was precontracted submaximally with phenylephrine (10 micromol/L). RESULTS: All PDE-5 inhibitors tested (0.001-10 micromol/L) relaxed phenylephrine-precontracted HCC with similar values of potency in a concentration-dependent manner. However, the maximal relaxations induced by tadalafil (83% +/- 4%) were significantly lower compared with sildenafil (107% +/- 5%) and vardenafil (111% +/- 3%). The NO synthesis inhibitor N-nitro-l-arginine methyl ester (100 micromol/L) caused significant rightward shifts in the concentration-response curves for sildenafil (4.0-fold), vardenafil (4.6-fold), and tadalafil (3.2-fold) in HCC tissue. The guanylyl cyclase inhibitor 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (10 micromol/L) also produced similar rightward shifts for these PDE-5 inhibitors. The cavernosal relaxations evoked by either acetylcholine or the NO donor glyceryl trinitrate were markedly potentiated by sildenafil, vardenafil, and tadalafil (0.1 micromol/L each). All PDE-5 inhibitors significantly increased the duration of electrical field stimulation-induced relaxations (8 Hz). CONCLUSIONS: Our findings have shown that sildenafil, vardenafil, and tadalafil relax HCC tissues in a concentration-dependent manner, but the maximal relaxation obtained with tadalafil was significantly lower than that obtained with sildenafil and vardenafil. Moreover, the PDE-5 inhibitors interacted with endogenous and exogenous NO, amplifying its HCC relaxation.
Assuntos
Carbolinas/farmacologia , Imidazóis/farmacologia , Relaxamento Muscular/efeitos dos fármacos , Óxido Nítrico/metabolismo , Pênis/enzimologia , Pênis/fisiologia , Inibidores da Fosfodiesterase 5 , Inibidores de Fosfodiesterase/farmacologia , Piperazinas/farmacologia , Sulfonas/farmacologia , Adolescente , Adulto , Idoso , Humanos , Masculino , Pessoa de Meia-Idade , Pênis/efeitos dos fármacos , Purinas/farmacologia , Citrato de Sildenafila , Tadalafila , Triazinas/farmacologia , Dicloridrato de Vardenafila , Adulto JovemRESUMO
Long-term propranolol treatment reduces arterial blood pressure in hypertensive individuals mainly by reducing peripheral vascular resistance, but mechanisms underlying their vasodilatory effect remain poorly investigated. This study aimed to investigate whether long-term propranolol administration ameliorates the impairment of relaxing responses of aorta and mesenteric artery from rats made hypertensive by chronic nitric oxide (NO) deficiency, and underlying mechanisms mediating this phenomenon. Male Wistar rats were treated with N(omega)-Nitro-L-arginine methyl ester (L-NAME; 20 mg/rat/day) for four weeks. DL-Propranolol (30 mg/rat/day) was given concomitantly to L-NAME in the drinking water. Treatment with L-NAME markedly increased blood pressure, an effect largely attenuated by DL-propranolol. In phenylephrine-precontracted aortic rings, the reduction of relaxing responses for acetylcholine (0.001-10 microM) in L-NAME group was not modified by DL-propranolol, whereas in mesenteric rings the impairment of acetylcholine-induced relaxation by L-NAME was significantly attenuated by DL-propranolol. In mesenteric rings precontracted with KCl (80 mM), DL-propranolol failed to attenuate the impairment of acetylcholine-induced relaxation by L-NAME. The contractile responses to extracellular CaCl2 (1-10 mM) were increased in L-NAME group, and co-treatment with DL-propranolol reduced this response in both preparations in most Ca2+ concentrations used. The NO2/NO3 plasma levels and superoxide dismutase (SOD) activity were reduced in L-NAME-treated rats, both of which were significantly prevented by DL-propranolol. In conclusion, propranolol-induced amplification of the relaxation to acetylcholine in mesenteric arteries from L-NAME-treated rats is sensitive to depolarization. Additional mechanisms involving blockade of Ca2+ entry in the vascular smooth muscle and increase in NO bioavailability contributes to beneficial effects of long-term propranolol treatment.
Assuntos
Anti-Hipertensivos/farmacologia , Aorta/efeitos dos fármacos , Hipertensão/fisiopatologia , Artérias Mesentéricas/efeitos dos fármacos , Óxido Nítrico/metabolismo , Propranolol/farmacologia , Vasodilatação/efeitos dos fármacos , Vasodilatadores/farmacologia , Acetilcolina/farmacologia , Animais , Anti-Hipertensivos/uso terapêutico , Aorta/enzimologia , Aorta/metabolismo , Aorta/fisiopatologia , Fatores Biológicos/metabolismo , Pressão Sanguínea/efeitos dos fármacos , Cálcio/metabolismo , Modelos Animais de Doenças , Relação Dose-Resposta a Droga , Inibidores Enzimáticos , Hipertensão/induzido quimicamente , Hipertensão/enzimologia , Hipertensão/metabolismo , Masculino , Artérias Mesentéricas/enzimologia , Artérias Mesentéricas/metabolismo , Artérias Mesentéricas/fisiopatologia , NG-Nitroarginina Metil Éster , Óxido Nítrico/sangue , Óxido Nítrico Sintase/antagonistas & inibidores , Óxido Nítrico Sintase/metabolismo , Nitroglicerina/farmacologia , Potássio/metabolismo , Propranolol/uso terapêutico , Ratos , Ratos Wistar , Superóxido Dismutase/sangue , Fatores de Tempo , Vasodilatadores/uso terapêuticoRESUMO
1. Propranolol has been prescribed successfully to patients with cardiovascular diseases, but the exact mechanisms by which it reduces peripheral vascular resistance have been poorly investigated. 2. The present study was designed to investigate the relaxing effects of propranolol in the rat isolated aorta and mesenteric artery, focusing on the contribution of the nitric oxide (NO)-cGMP pathway and calcium entry blockade. Relaxation responses to propranolol were obtained in precontracted rat aortic and mesenteric artery rings. 3. DL-Propranolol (10-100 micromol/L) produced concentration-dependent relaxations in the aorta and mesenteric artery rings with intact endothelium. The isomers D- and L-propranolol produced relaxation responses that were equipotent to the racemic mixture. 4. Metoprolol (10-100 micromol/L) produced slight relaxations, whereas atenolol (10-100 micromol/L) had no relaxant activity. 5. The NO inhibitor N(G)-nitro-L-arginine methyl ester (100 micromol/L) and the soluble guanylate cyclase inhibitor 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (1 micromol/L), as well as removal of the endothelium, significantly reduced the relaxation responses induced by the lower concentrations of propranolol without affecting maximal responses. In addition, DL-propranolol markedly increased cGMP levels in endothelium-intact preparations. 6. In Ca(2+)-free Krebs' solution, DL-propranolol (10-100 micromol/L) caused marked rightward shift in the concentration-response curves to CaCl(2), with a decrease of maximal responses in tissues with either intact or denuded endothelium. Nifedipine (1 micromol/L) in combination with DL-propranolol virtually abolished the CaCl(2)-induced contractile responses. 7. The relaxation responses induced by DL-propranolol were significantly reduced in aortic and mesenteric rings precontracted with phorbol-12,13-dibutyrate (1 micromol/L). 8. In conclusion, DL-propranolol relaxes arterial smooth muscle by mechanisms involving activation of the NO-cGMP pathway and calcium influx blockade, independent of beta-adrenoceptor blockade.
Assuntos
Aorta/efeitos dos fármacos , Cálcio/metabolismo , Artérias Mesentéricas/efeitos dos fármacos , Óxido Nítrico/metabolismo , Propranolol/farmacologia , Vasodilatação , Animais , Aorta/enzimologia , Bloqueadores dos Canais de Cálcio/farmacologia , GMP Cíclico/metabolismo , Relação Dose-Resposta a Droga , Endotélio Vascular/efeitos dos fármacos , Endotélio Vascular/enzimologia , Inibidores Enzimáticos/farmacologia , Guanilato Ciclase/antagonistas & inibidores , Guanilato Ciclase/metabolismo , Técnicas In Vitro , Masculino , Artérias Mesentéricas/enzimologia , Músculo Liso Vascular/efeitos dos fármacos , Músculo Liso Vascular/enzimologia , NG-Nitroarginina Metil Éster/farmacologia , Nifedipino/farmacologia , Óxido Nítrico Sintase/antagonistas & inibidores , Óxido Nítrico Sintase/metabolismo , Oxidiazóis/farmacologia , Quinoxalinas/farmacologia , Ratos , Vasodilatadores/farmacologiaRESUMO
The compound BAY 41-2272 stimulates the soluble guanylyl cyclase in a nitric oxide (NO)-independent manner. We have investigated the potency and efficacy of BAY 41-2272 in the rat anococcygeus muscle, as well as the effects of BAY 41-2272 on NO-mediated anococcygeus relaxations. BAY 41-2272 (0.01-10 microM) potently relaxed precontracted anococcygeus muscle strips, with a pEC(50) value of 6.44 +/- 0.03 and maximum response of 100 +/- 2%. The soluble guanylyl cyclase inhibitor 1H-[1,2,4]-oxidiazolo[4,3-a] quinoxalin-1-one (ODQ, 1 microM) and the NO inhibitor N(omega)-nitro-L-arginine methyl ester (L-NAME, 100 microM) caused significant rightward shifts in the concentration-response curves to BAY 41-2272. The phosphodiesterase type-5 inhibitor tadalafil (0.1 microM) markedly enhanced the relaxations evoked by BAY 41-2272. In addition, BAY 41-2272 increased the duration of nitrergic relaxations by approximately 55%. The relaxations induced by glyceryl trinitrate were also significantly potentiated by BAY 41-2272. In conclusion, BAY 41-2272 interacts with endogenous and exogenous NO causing a potent relaxation of rat anococcygeus muscle.
Assuntos
Relaxamento Muscular/efeitos dos fármacos , Músculo Liso/efeitos dos fármacos , Óxido Nítrico/farmacologia , Pirazóis/farmacologia , Piridinas/farmacologia , Receptores Citoplasmáticos e Nucleares/metabolismo , Animais , Carbacol/farmacologia , Carbolinas/farmacologia , Colforsina/farmacologia , AMP Cíclico/metabolismo , GMP Cíclico/metabolismo , Relação Dose-Resposta a Droga , Sinergismo Farmacológico , Estimulação Elétrica , Ativação Enzimática/efeitos dos fármacos , Inibidores Enzimáticos/farmacologia , Guanilato Ciclase , Contração Muscular/efeitos dos fármacos , Músculo Liso/fisiologia , NG-Nitroarginina Metil Éster/farmacologia , Doadores de Óxido Nítrico/farmacologia , Óxido Nítrico Sintase/antagonistas & inibidores , Óxido Nítrico Sintase/metabolismo , Nitroglicerina/farmacologia , Oxidiazóis/farmacologia , Quinoxalinas/farmacologia , Ratos , Ratos Wistar , Receptores Citoplasmáticos e Nucleares/antagonistas & inibidores , Guanilil Ciclase Solúvel , Tadalafila , Tetrodotoxina/farmacologiaRESUMO
1. The compound BAY 41-2272 (5-cyclopropyl-2-[1-(2-fluoro-benzyl)-1H-pyrazolo[3,4-b]pyridin-3-yl]-pyrimidin-4-ylamine) has been described as a potent, nitric oxide (NO)-independent, stimulator of soluble guanylate cyclase. In the present study, the mechanisms underlying the relaxant effect of BAY 41-2272 in endothelium-intact and -denuded precontracted rabbit aortic rings were investigated. 2. Male New Zealand white rabbits were anaesthetized with pentobarbital sodium. Aortic rings were transferred to 10 mL organ baths containing oxygenated and warmed Krebs' solution. Tissues were connected to force-displacement transducers and changes in isometric force were recorded. Aortic rings were precontracted submaximally with phenylephrine (1 micromol/L). 3. The addition of BAY 41-2272 (0.01-10 micromol/L) to the organ bath produced concentration-dependent relaxations of the aortic rings with a higher potency in endothelium-intact (pEC50 6.59 +/- 0.05) compared with endothelium-denuded (pEC50 6.19 +/- 0.04; P < 0.05) preparations. No differences in maximal responses were observed in either preparation. The NO synthesis inhibitor NG-nitro-L-arginine methyl ester (100 micromol/L) produced a 2.1-fold rightward shift in endothelium-intact (P < 0.01) rings, but had no effect in endothelium-denuded rings. The soluble guanylate cyclase inhibitor 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ; 1 micromol/L) caused significant rightward shifts of the concentration-response curves to BAY 41-2272 of 4.9- and 2.6-fold in endothelium-intact and -denuded rings, respectively. The phosphodiesterase-5 inhibitor sildenafil (0.1 micromol/L) significantly potentiated the relaxant effects of BAY 41-2272 in both endothelium-intact and -denuded rings. 4. At 1 micromol/L, BAY 41-2272 significantly elevated the aortic cGMP content above basal levels in both endothelium-intact and -denuded rings. Furthermore, ODQ reduced BAY 41-2272-elicited increases in cGMP content by 17 and 90% in endothelium-intact and -denuded rings, respectively (P < 0.01). 5. In conclusion, BAY 41-2272 potently relaxes endothelium-intact and -denuded rabbit aortic rings. The basal release of endothelium-derived NO enhances BAY 41-2272-induced relaxations, suggesting a synergistic effect of BAY 41-2272 and NO on soluble guanylate cyclase. In addition, the endothelium-independent relaxation involves both GMP-dependent and -independent mechanisms.
Assuntos
Aorta/efeitos dos fármacos , Guanilato Ciclase/efeitos dos fármacos , Pirazóis/farmacologia , Piridinas/farmacologia , Vasodilatação/efeitos dos fármacos , Animais , Relação Dose-Resposta a Droga , Ativação Enzimática/efeitos dos fármacos , Técnicas In Vitro , Masculino , NG-Nitroarginina Metil Éster/farmacologia , Óxido Nítrico/fisiologia , Oxidiazóis/farmacologia , Piperazinas/farmacologia , Purinas , Quinoxalinas/farmacologia , Coelhos , Transdução de Sinais , Citrato de Sildenafila , SulfonasRESUMO
OBJECTIVES: To evaluate the contractile and relaxing responses in rat corpus cavernosum (RCC) from rats after 8 weeks of run training, because erectile function is highly dependent on nitric oxide (NO) from nitrergic fibers or endothelium. Physical activity enhances NO production and improves endothelial function, with beneficial effects on cardiovascular disease. METHODS: The training program consisted of 8 weeks of run training, 5 days/wk, and each session lasted 60 minutes. The RCC was isolated, and concentration-response curves to NO, acetylcholine, sodium nitroprusside, phenylephrine, and endothelin were obtained. The excitatory and inhibitory effects of electrical field stimulation (2 to 32 Hz) were also evaluated. RESULTS: NO (0.1 to 100 microM) and sodium nitroprusside (0.01 to 1000 microM) produced a relaxing effect in RCC in a dose-dependent manner, with the maximal responses to NO (control 62% +/- 4%, trained 88% +/- 3%) and sodium nitroprusside (control 83% +/- 3%, trained 95% +/- 2%) significantly enhanced after 8 weeks of run training. However, acetylcholine-induced relaxations were not affected by exercise. Similarly, electrical field stimulation-induced relaxations were significantly increased in RCC from trained rats at 2 Hz (control 2.4% +/- 0.3%, trained 4.2% +/- 0.5%) and 4 Hz (control 5.3% +/- 1.2%, trained 12.5% +/- 1.7%). The contractile sensitivity of RCC to phenylephrine (0.01 to 100 microM) and endothelin (0.01 to 100 nM) was not modified by training exercise. CONCLUSIONS: Our findings suggest that run training enhances functional responses in rat RCC that involves increases in the NO-cyclic guanosine monophosphate signaling pathway by endothelium-independent mechanisms that is not accompanied by changes in contractile sensitivity.