Effects of various nitric oxide-donating drugs on adrenergic tension of human seminal vesicles in vitro (original) (raw)
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Urology, 2002
To evaluate the effects of the nitric oxide (NO)-donating drugs sodium nitroprusside, S-nitroso-glutathione (GSNO), S-nitroso-N-acetylcysteineetylester (SNACET), and linsidomine (SIN-1), as well as the adenylyl cyclase-stimulating agent forskolin, on electrically induced contractions and on tissue levels of cyclic guanosine monophosphate (cGMP) and cyclic adenosine monophosphate (cAMP) of isolated human seminal vesicle strip preparations. The significance of the L-arginine-NO-cGMP pathway in the regulation of smooth muscle tone in the human genitourinary tract has been well established; however, information on the relevance of NO-mediated signal transduction in the functional control of mammalian seminal vesicles is still sparse. Seminal vesicle strip preparations were applied to an organ bath system under standard conditions. Phasic contractions were induced by electrical field stimulation (frequency 80 Hz, amplitude 10 V, single pulse 1 ms, total pulse duration 1 second, pause 90 seconds). After stable contraction amplitudes had been reached, the drugs were added in a cumulative manner (0.001 to 10 microM), and the isometric responses were registered. After drug exposure, freezing, tissue homogenization, and extraction of cyclic nucleotides, cAMP and cGMP were measured by means of enzyme-linked immunosorbent assays. Electrical field stimulation-induced amplitudes were attenuated by the drugs in a dose-dependent manner. The rank order of potency was GSNO > sodium nitroprusside > forskolin > SNACET > or = SIN-1. The relaxing effect of GSNO was antagonized in the presence of 10 microM of guanylyl cyclase inhibitor methylene blue. The inhibitory effects of GSNO, sodium nitroprusside, and forskolin on the contractile activity were paralleled by an increase in tissue cGMP (2 to 100-fold) and cAMP (7 to 9-fold). Our results strongly support the hypothesis that the contractility of human seminal vesicles is in part regulated by the NO-cGMP-cascade. This may give a rationale for the use of S-nitrosothiols, such as GSNO, in the pharmacotherapy of hyperexcitatory disturbances of ejaculation.
Effects of autonomic drugs on contractions of rat seminal vesicles in vivo
Reproduction, 1984
Various autonomic drugs were placed on the peritoneal covering of the seminal vesicles of anaesthetized rats. Adrenaline (which stimulates the \g=a\-,\g=b\1-and \ g = b \ 2 \ x = r e q-\ adrenoceptors) and phenylephrine (an \g=a\-stimulatingagent) produced a sudden increase in tonus and in the amplitude and frequency of contractions. Phentolamine (an \ g = a \ \ x = r e q-\ blocker) prevented these effects, whereas propranolol (a \g=b\1and \g=b\2-blocker) did not. Phentolamine also abolished the seminal vesicle response to electrical stimulations. Terbutaline (a \g=b\2-stimulating agent) did not affect the spontaneous activity. There were no differences between the effects of terbutaline alone and those of terbutaline in the presence of propranolol. Moreover, propranolol did not block the contractile response of the gland to adrenaline or to electrical stimulation. These results indicate that \ g=a\ \ x =r eq-\ adrenergic receptors are present in the muscle cell membrane of the rat seminal vesicle. The effects of acetylcholine were similar to those produced by adrenaline or phenylephrine although of smaller magnitude. Atropine prevented the effects of acetylcholine, indicating that they are of the muscarinic type.
European Urology, 2002
Objectives: The discovery of nitric oxide (NO) as one of the major effectors in penile erectile function has led to the development of various drugs which are able to elevate intracellular levels of cGMP. Recently, a novel class of NO donors have been developed, exempli®ed by S-nitroso-glutathione (GSNO) and S-nitroso-N-acetylcysteineethylester (SNACET), as well as compounds combining both phosphodiesterase inhibitory and NO donating activity, such as NCX 911 (sildena®l nitrate). In our study, we assessed the effects of GSNO, SNACET and NCX 911 on adrenergic tension and electrically induced relaxation of isolated human corpus cavernosum (HCC) and the in vitro formation of cGMP. Effects were compared to those of sodium nitroprusside (SNP) and sildena®l citrate. Materials and Methods: Using the organ bath technique, drug effects were investigated on norepinephrine-induced tension and electrically induced relaxation of HCC. HCC strips were exposed to increasing concentrations of the compounds (0.01/0.1±10/100 mM) and the accumulation of cGMP was determined by means of a radioimmunoassay. Results: Relaxation of HCC induced by means of electrical ®eld stimulation (EFS) was abolished by tetrotodoxin, guanylyl cyclase inhibitor ODQ and nitric oxide synthase inhibitor L-NNA. Adrenergic tension of HCC strips was dose-dependently reversed by the drugs. The rank order of potency was: SNP > GSNO > NCX 911 > sildenafil > SNACET. Compounds also dose-dependently increased EFS-induced amplitudes of relaxation (SNP > NCX 911 > sildenafil > SNACET/GSNO). Relaxing effects of the drugs were paralleled by an increase in tissue levels of cGMP. Conclusion: Our results provide a rationale for future use of NCX 911 and S-nitrosothiols in the pharmacotherapy of erectile dysfunction (ED). Since the compounds are assumed to exert no considerable hemodynamic effects, they might be developed into new oral treatments for ED. #
European Journal of Pharmacology, 2012
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 (20 mg/rat/day) concomitantly with BAY 41-2272 (10 mg/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.
Urology, 2003
To determine the effectiveness of BAY 41-2272 on penile erections in an in vivo rabbit model. The nitric oxide (NO)-dependent increase of intracellular cyclic guanosine monophosphate (cGMP) by cGMP-phosphodiesterase (PDE5) inhibition has been shown to be an effective mechanism in the treatment of erectile dysfunction. Direct, NO-independent stimulation of soluble guanylyl cyclase should also lead to elevated cGMP levels in tissues and could be an attractive alternative therapeutic option for the treatment of erectile dysfunction. BAY 41-2272 is a novel non-NO-based direct stimulator of soluble guanylyl cyclase that activates purified enzyme in a synergistic fashion with NO. Methods. BAY 41-2272 was administered to conscious rabbits intravenously (IV) and orally (PO). Erection was assessed in a time-dependent manner by measuring the length of the uncovered penile mucosa. Erections were evaluated in the absence and presence of NO (with intravenous sodium nitroprusside [SNP] as the NO donor). Results. BAY 41-2272 only induced weak penile erections in conscious rabbits after IV (1 mg/kg) and PO (10 mg/kg) administration in the absence of an NO donor. However, the efficacy of BAY 41-2272 was potentiated by the simultaneous administration of SNP. Through simultaneous SNP administration, the effective doses of BAY 41-2272 were reduced significantly (minimal effective dose 0.1 mg/kg IV and 1 mg/kg PO). Conclusions. The results of this study clearly demonstrated the effect of BAY 41-2272 on penile erection in the conscious rabbit model after PO and IV administration. The time-course and onset of erection was concurrent with the stimulation by exogenous NO (SNP), suggesting that this new pharmacologic mechanism of soluble guanylyl cyclase stimulation could be used in the treatment of erectile dysfunction. Because the effect is increased by SNP, it can be expected that BAY 41-2272 would have enhanced activity during sexual arousal, when NO is produced endogenously. UROLOGY 61: 464-467, 2003.
Sperm nitric oxide and motility: the effects of nitric oxide synthase stimulation and inhibition
Molecular Human Reproduction, 1997
Nitric oxide (NO) is synthesized from L-arginine by a family of enzymes known as the nitric oxide synthases (NOS). We have recently shown a NOS similar to constitutive brain NOS (bNOS) and endothelial NOS (ecNOS) to be present in spermatozoa. The aim of this study is to investigate NO production by human spermatozoa and the effects of stimulation and inhibition of NOS. This was carried out using the Iso-NO, an isolated NO meter and sensor, which provides rapid, accurate and direct measurements of NO. Semen samples with normozoospermic and asthenozoospermic profiles were prepared using a direct swim-up technique. Basal concentrations of NO and stimulated NO production were measured after exposure to the calcium ionophore (A23187; 0.01-10 µM) a potent activator of constitutive NOS. NO production in human spermatozoa was significantly increased by the addition of A23187 30 seconds after stimulation. Furthermore, this response was greatly diminished by pre-incubating the samples with competitive inhibitors of L-arginine, the substrate for NOS, before treatment with calcium ionophore. In the presence of N G-nitro-L-arginine methyl ester (L-NAME), N G-nitro-L-arginine (L-NA) or N G-methyl-L-arginine (L-NMMA; all at 10 µM), NO production was inhibited with a rank order of potency L-NAME Ͼ L-NMMA Ͼ L-NA which is in accordance with the inhibition of an endothelial type of constitutive NOS.
Inhibition of tonic contraction--a novel way to approach erectile dysfunction
Journal of andrology
Experiments from this laboratory have demonstrated that vasoconstriction in the cavernosal circulation is mediated, in part, by the RhoA/Rho-kinase calcium-sensitization pathway. When RhoA/Rho-kinase signaling is inhibited with Y-27632 in cavernosal smooth muscle, the intracavernosal pressure (ICP) is markedly elevated without a significant change in mean arterial pressure (MAP). To explain how erection can occur in the presence of this strong vasoconstrictive signal, we have suggested that nitric oxide (NO) induces vasodilation, leading to erection by directly inhibiting activity of the RhoA/Rho-kinase pathway. The following discussion summarizes the importance of Rho-kinase signaling in the erectile response and introduces its possible clinical value in 2 animal models of erectile dysfunction (ED) (severe hypogonadism and hypertension). In addition, we suggest that topical application of Y-27632 could be an effective mode of treatment for ED.
Nitric oxide release in penile corpora cavernosa in a rat model of erection
The Journal of Physiology, 1999
Nitric oxide (NO) is thought to play an important regulatory role in penile erection. Several studies have found the enzymatic activity generating NO (NO synthase; NOS) in the penile erectile bodies, located in both nerve fibres and endothelial cells (Burnett et al. 1992; Dail et al. 1995). The relaxation of cavernous smooth muscle, a prime requirement for the initiation and maintenance of penile erection (Saenz de Tejada et al. 1991), is highly susceptible to pharmacological manipulations of NO. In organ bath experiments, precontracted cavernosal tissue strips from various sources, including man, have been consistently found to relax in response to the addition of NO releasing substances (Ignarro et al. 1990; Rajfer et al. 1992). On the contrary, both the endothelium-dependent and the neurogenic relaxation of cavernosal muscle strips precontracted by á_adrenergic agonists are suppressed by drugs inhibiting the synthesis or actions of NO, such as NOS inhibitors, NO scavengers, and soluble guanylate cyclase inhibitors (
International Journal of Impotence Research, 2001
Studies in this laboratory are designed to determine the effects of vasoconstrictor agents on the erectile response in rats. We have previously demonstrated that the vasoconstrictor effect of endothelin-1 (ET-1) is sharply reduced by erection and by nitric oxide (NO) administration. The present study was performed to determine if vasoconstriction, resulting from a-adrenergic stimulation, is altered by erection and NO. During continuous monitoring of corpus cavernosum pressure (CCP) and mean arterial pressure (MAP), erection was induced by electrical stimulation of the autonomic ganglion for the innervation of the penis. When the a-adrenergic agonist methoxamine (METH, 10 m mgakg) was injected before erection (ie, into the non-erect penis), the subsequent erectile response (CCPaMAP) was signi®cantly reduced from 0.68 AE 0.03 before METH to 0.34 AE 0.08 after METH. Injection of METH into the erect penis (ie, during erection) reduced the vasoconstrictor action of METH; CCPaMAP was 0.74 AE 0.02 before METH and 0.55 AE 0.05 after METH (P`0.05). The vasoconstrictor action of METH was slightly reduced when given in conjunction with NOR-1, a NO donor drug; CCPaMAP was 0.70 AE 0.05 before METH, 0.55 AE 0.09 after METH but this change was not signi®cant. These results demonstrate that the response to a aadrenergic stimulation is attenuated during erection in response to ganglionic stimulation. Furthermore, it appears that NO, produced during erection, may serve to override agonist-induced vasoconstriction. These results support our hypothesis that NO acts to directly stimulate relaxation of cavernous smooth muscle and to inhibit the vasoconstrictor actions of agents like ET-1 and a-adrenergic agonists including norepinephrine.