RESUMEN
Results from basic research implicate a role for bioactive peptides in controlling the mammalian lower urinary tract. Although various peptides are assumed to be involved in the potentiaton or inhibition of cholinergic or purinergic activity in the urinary bladder, there is still much controversy regarding the mode of action and functional significance of such peptides in detrusor smooth muscle. Thus, we evaluated the functional effects of atrial natriuretic peptide (ANP), calcitonin gene related peptide (CGRP), endothelin 1 (ET-1), substance P (SP) and vasoactive intestinal polypeptide (VIP) on isolated strip preparations of human detrusor smooth muscle and determined the presence of those peptides in the human detrusor by means of immunohistochemistry. The effects of peptides on isometric tension of isolated detrusor strip preparations and on tissue levels of cyclic nucleotides cAMP and cGMP were compared to those of adenylyl cyclase activator forskolin (F), nitric oxide donor Na(+)-nitroprusside (SNP) and non-specific phosphodiesterase (PDE) inhibitor papaverine (P). The effects of the compounds on isometric tension of isolated human detrusor smooth muscle were examined using the organ bath technique. To determine time- and dose-dependent effects on cyclic nucleotide levels, bladder strips were exposed to increasing doses of F, SNP, P, ANP, CGRP and VIP, then rapidly frozen in liquid nitrogen and homogenised in the frozen state. cAMP and cGMP were extracted and assayed using specific radioimmunoassays. The presence of peptides was investigated by light microscopy using the Avidin-Biotin-Complex (ABC) method. F, P and VIP most effectively reversed the carbachol-induced tension of isolated human detrusor strips. Relaxing effects of ANP, CGRP and SNP were negligible. In contrast, ET-1 and SP elicited dose-dependent contractions of the tissue. The relaxing effects of F, P and VIP were accompanied by an increase in cAMP and cGMP levels, respectively. Light microscopy revealed positive immunostaining for CGRP, ET 1, VIP and SP in sections of the detrusor muscle coat. Our results suggest a possible importance of ET 1, SP and VIP in regulating detrusor smooth muscle contraction and relaxation. Even if a peptide is not synthesised, stored or released in a smooth muscle tissue and is, therefore, unable to reach its target cells under physiologic conditions, a functional effect on the tissue might be mediated by peptide-binding to specific cell surface receptors.
Asunto(s)
Músculo Liso/patología , Músculo Liso/fisiopatología , Péptidos/fisiología , Enfermedades de la Vejiga Urinaria/patología , Enfermedades de la Vejiga Urinaria/fisiopatología , Factor Natriurético Atrial/análisis , Péptido Relacionado con Gen de Calcitonina/análisis , Endotelina-1/análisis , Femenino , Humanos , Técnicas In Vitro , Masculino , Contracción Muscular/fisiología , Sustancia P/análisis , Vejiga Urinaria/patología , Vejiga Urinaria/fisiopatología , Péptido Intestinal Vasoactivo/análisisRESUMEN
Results from basic research scrutiny indicate a role for non-adrenergic, non-cholinergic transmitters, among which there are various peptides, in the physiology of normal male sexual function. Nevertheless, it is not yet known which particular peptides are essentially involved in maintaining sexual arousal and regulating penile tumescence and rigidity in adult males. Vasoactive intestinal polypeptide (VIP), a peptide with smooth muscle relaxing properties, is considered to be one of the factors that contributes to such control. The present study was performed to evaluate the significance of VIP in normal male sexual function. We determined the plasma levels of VIP in the systemic and cavernous blood of 54 healthy adult male volunteers, who were exposed to visual and tactile erotic stimuli in order to elicit penile tumescence and erection. Whole blood was aspirated from the corpus cavernosum and the cubital vein during penile flaccidity, tumescence, rigidity and detumescence, and VIP was quantified in plasma aliquots by means of a radioimmunoassay. Of the 54 volunteers, 16 were permitted to masturbate and ejaculate, and blood was then again withdrawn from the cavernous meshwork and the cubital vein in order to measure VIP. All VIP levels were registered within the normal physiological range from 3.0-30 pmol/l. No increase in median VIP plasma levels was observed in the systemic and cavernous blood when the flaccid penis became rigid. During penile detumescence, mean cavernous VIP level increased to 11.9+/-7.8 pmol/l (baseline: 8.6+/-3.0 pmol/l), whereas VIP remained unaltered in the systemic circulation. Following ejaculation, mean VIP level in the cavernous blood was elevated to 25.3+/-10.9 pmol/l, whereas, in the systemic blood, no significant changes were registered. Our results support the hypothesis that VIP plays a functional role in the mechanism of male sexual arousal. Nevertheless, our data indicate that the peptide is not the main non-adrenergic, non-cholinergic mediator of penile tumescence and rigidity in human males.
Asunto(s)
Erección Peniana/fisiología , Pene/irrigación sanguínea , Péptido Intestinal Vasoactivo/sangre , Adulto , Humanos , Masculino , Valores de ReferenciaRESUMEN
OBJECTIVES: 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. METHODS: 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. RESULTS: 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). CONCLUSIONS: 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.