Effects of endopeptidase inhibition on the contraction-relaxation response of isolated human vaginal tissue.

INTRODUCTION.: Vasoactive peptides, such as bradykinin, C-type natriuretic peptide (CNP), vasoactive intestinal polypeptide (VIP), and endothelin 1 (ET-1), are assumed to be involved in the control of female genital vascular and nonvascular smooth muscle. Tissue levels of said peptides are controlled by the activity of endopeptidase enzymes. Theoretically, in female genital tissues, inhibiting the degradation of bradykinin, CNP, and VIP, or the conversion of Big ET-1 into ET-1 should result in an enhancement in smooth muscle relaxation and, thus, an improvement in sexual response. AIM.: Elucidate the effects of the endopeptidase inhibitor KC 12615 on the contraction/relaxation response of isolated human vaginal smooth muscle to Big ET-1, bradykinin, CNP, or VIP. METHODS.: Tissue bath experiments were carried out to ascertain the responses of human vaginal tissue challenged by ET-1 (0.1 µM) to increasing concentrations of bradykinin, CNP, and VIP (0.01 µM, 0.1 µM, and 1 µM, respectively). The effects were also evaluated following preexposure to KC 12615 (10 µM, for 20 minutes). MAIN OUTCOME MEASURES.: Measure the effects of KC 12615 on the relaxation of isolated human vaginal smooth muscle brought about by bradykinin, CNP, or VIP and the contraction mediated by Big ET-1. RESULTS.: The tension induced by ET-1 was reversed by bradykinin, CNP, or VIP (-25 ± 6.6%, -13.3 ± 2.2%, and -17.6 ± 10%, respectively). Big ET-1 induced contraction of the vaginal tissue. Preexposure of the tissue to KC 12615 increased the relaxation exerted by bradykinin, CNP, or VIP (to -39.2 ± 5.8%, -40.7 ± 7.3%, and -44.6 ± 19%, respectively). The contraction induced by Big ET-1 was attenuated in the presence of KC 12615 (to approximately 25% of the initial response). CONCLUSION.: Inhibition of endopeptidase activity can antagonize the contraction of human vaginal tissue induced by Big ET-1 and increase the relaxation induced by vasoactive endogenous peptides.

Endogenous vasoactive peptides and the human vagina--a molecular biology and functional study.

INTRODUCTION: Endogenous peptides, such as vasoactive intestinal polypeptide (VIP), C-type natriuretic peptide (CNP), and bradykinin (BK), have been proposed to play a role in the female sexual arousal response by exerting relaxation of clitoral, labial, and vaginal smooth muscle. While the effects of endogenous peptides on the human male erectile tissue have already been described, only very few studies have been conducted to investigate the peptidergic control of female genital tissues, including the vagina. AIMS: To elucidate the expression of mRNA specifically encoding for peptide receptors in the human vagina and the effects of VIP, CNP, and BK on the tension induced by endothelin-1 (ET-1) of isolated human vaginal wall smooth muscle. The production of cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP) in response to exposure of the tissue to the peptides was also measured. METHODS: The expression of mRNA encoding for receptor proteins specific for VIP, CNP, and BK were investigated by means of molecular biology (reverse transcriptase polymerase chain reaction [RT-PCR] analysis). Using the organ bath technique, the effects of VIP, CNP, and BK (0.1 nM to 1 µM) on the tension induced by 0.1 µM ET-1 of human vaginal strips were investigated. The tissue was also exposed to three different concentrations of VIP, CNP, and BK (0.01 µM, 0.1 µM, 1 µM) and the production of cAMP and cGMP determined by means of radioimmunoassays. MAIN OUTCOME MEASURES: Characterize the expression of peptide receptors in the human vagina and measure the relaxation exerted by BK, CNP, and VIP on the contraction induced by ET-1 of isolated human vaginal tissue. In addition, the effects of the peptides on the production of cAMP and cGMP were also elucidated. RESULTS: RT-PCR analysis revealed the expression of mRNA transcripts encoding for the VIP receptors VIP1R/vasoactive intestinal polypeptide receptor type 1 (VPAC1) and VIP2R/VPAC2, CNP receptors natriuretic peptide receptor type A (NPRA), natriuretic peptide receptor type B (NPRB) and natriuretic peptide receptor type C (NPRC), and BK receptor B2R. The tension induced by ET-1 was reversed by the peptides with the following rank order of efficacy: BK (21.7%) > VIP (20.9%) > CNP (13.3%). The relaxing effects of VIP and BK were paralleled by a 4.8-fold and fivefold increase in cAMP, while the production of cGMP was stimulated 38-fold and 119-fold in the presence of CNP or BK, respectively. CONCLUSION: Our results are in support of the hypothesis that endogenous peptides may contribute to the control of human vaginal smooth muscle tone through the involvement of the cyclic nucleotide-dependent pathways.

Exposure of human seminal vesicle tissue to phosphodiesterase (PDE) inhibitors antagonizes the contraction induced by norepinephrine and increases production of cyclic nucleotides.

OBJECTIVES: To investigate further the role of phosphodiesterase (PDE) isoenzymes in the control of human seminal vesicle (SV) smooth muscle contractility, we examined the functional responses of isolated SV tissue to various PDE inhibitors. It has been suggested that the application of inhibitors of the PDE type 5 may facilitate SV smooth muscle relaxation and, subsequently, retard ejaculatory response. METHODS: Using the organ bath technique, strip preparations of human SV were exposed for 5 minutes to 1 µM of the PDE inhibitors milrinone (PDE3 inhibitor), rolipram, Ro 20-1724 (PDE4 inhibitors), and sildenafil (PDE5 inhibitor). Norepinephrine (NE, alpha agonist) was then added (0,1 µM, 1 µM, and 10 µM) and isometric responses were recorded. A contraction-response curve to NE in the absence of PDE inhibitors was also generated. Drug effects on the production of cyclic adenosine monophosphate (AMP) and cyclic guanosine monophosphate (GMP) were measured by means of radioimmunometric assays. RESULTS: The contraction induced by NE was effectively antagonized by 1 µM of rolipram (83.3% inhibition), Ro 20-1724 (72.3% inhibition), sildenafil (41.6% inhibition), and milrinone (37.5% inhibition). The inhibition of force generation was paralleled by a 1.6-fold to 2.8-fold increase in tissue cyclic AMP (induced by milrinone, rolipram, Ro 20-1724), and a 12-fold rise in cyclic GMP (induced by sildenafil). CONCLUSION: The findings demonstrate that PDE inhibitors can counteract the contraction of human SV mediated by alpha-adrenergic receptors and enhance levels of cyclic nucleotides. This might be of importance with regard to the identification of new options for the pharmacological treatment of premature ejaculation.

Characterization of the effects of various drugs likely to affect smooth muscle tension on isolated human seminal vesicle tissue.

OBJECTIVES: To investigate the effects of different classes of drugs on the isometric tension of isolated human seminal vesicle (SV) tissue. The contractility of human SV contributes to the process of seminal emission during ejaculation. Different endogenous compounds, such as serotonin (5-HT), adenosine triphosphate (ATP), and nitric oxide, have been suggested to be involved in the control of contraction and relaxation of human SV smooth muscle. However, only limited data are available regarding the effects of compounds known to affect smooth musculature on SV contractile activity. METHODS: Using the organ bath technique, the effects of increasing concentrations (10 nm-1 microm/10 microm) of norepinephrine (NE), phenylephrine, endothelin 1, ATP, and 5-HT on human SV tissue at basal tension were studied. In another set-up, SV strip preparations were preincubated with prazosin (alpha-adrenergic blocker), nifedipine and verapamil (Ca(2+)-channel blockers), 2-aminoethoxydiphenyl borate [inositol 1,4,5-trisphosphate (IP(3)) antagonist], cromakalim (K(+)-channel opener), or Y-27632 (ROK inhibitor) (1 microm each, for 10 minutes), followed by the application of NE (0.1 microM, 1 microM, and 10 microm). RESULTS: SV smooth muscle was most effectively contracted by NE (mean = 75% of calibrated scale), phenylephrine (mean = 82% of calibrated scale), and endothelin 1 (mean = 70% calibrated scale), whereas only minor responses to ATP (mean = 10.65% calibrated scale) and 5-HT (mean = 6.3% calibrated scale) were observed. The contraction induced by NE was significantly inhibited after pre-exposure of the tissue to prazosin (-92.4%), cromakalim (-83.7%), 2-aminoethoxydiphenyl borate (-43.1%), Y-27632 (-42.8%), and nifedipine (-32.7%). CONCLUSIONS: alpha-adrenoceptor antagonism, activation of potassium channels, and inhibition of Rho-kinase decrease the sympathetic contraction of SV smooth muscle. This might be of significance with regard to the identification of new pharmacologic avenues to affect the male ejaculatory system.

Evaluating the role of the serotoninergic system in the control of human seminal vesicle smooth muscle-an in vitro approach.

INTRODUCTION: It has been suggested that serotonin re-uptake inhibitors (SRIs) may retard the ejaculatory response by acting directly on the seminal vesicle (SV) and ductus deferens smooth muscle. However, until now, only a very few experimental studies have investigated such potential local (peripheral) effects. AIM: To elucidate the effects of serotonin (5-HT) and the SRIs clomipramine, fluoxetine and imipramine on the tension induced by norepinephrine (NE) of isolated human SV smooth muscle, as well as on the production of tissue cyclic AMP and cyclic GMP. MAIN OUTCOME MEASURES: To measure the inhibition exerted by serotonin and SRIs clomipramine, fluoxetine, and imipramine on the contractile response of isolated SV tissue. In addition, the effects of the drugs on the turn-over of cyclic nucleotides cAMP and cGMP were also elucidated. METHODS: The effects of the cumulative addition of serotonin and the SRIs clomipramine, fluoxetine and imipramine (1 nM-10 microM) on the tension induced by the alpha(1)-adrenoceptor agonist NE (10 microM) of SV strip preparations were studied using the organ bath technique. Cyclic AMP and cyclic GMP were measured by means of specific radioimmunoassays. RESULTS: The tension induced by NE was dose-dependently reversed by the drugs tested. The rank order of efficacy was: imipramine > or = fluoxetine > or = clomipramine > serotonin. Mean reversion of tension was measured between 66 +/- 6.6% and 52 +/- 6.6%. These effects were paralleled by a 1.3-fold to 2.7-fold increase in tissue cAMP in response to exposure to the drugs. In contrast, no significant enhancement in cGMP was noted. CONCLUSIONS: The findings, for the first time, present evidence that SRIs may antagonize the sympathetic contraction of SV smooth muscle via stimulation of tissue cyclic AMP.

Efficacy and safety of tamsulosin hydrochloride compared to doxazosin in the treatment of Indonesian patients with lower urinary tract symptoms due to benign prostatic hyperplasia.

AIM: The objective of the study was to compare the efficacy and safety of tamsulosin hydrochloride and doxazosin in patients with lower urinary tract symptoms (LUTS) due to benign prostatic hyperplasia (BPH). METHODS: The safety and efficacy of tamsulosin (0.2 mg) and doxazosin (2 mg) was determined after once daily administration for 6 weeks in an open-label, randomized, multicenter study of 101 men with BPH. The International Prostatic Symptom Score (IPSS), maximal urinary flow rates (Qmax), average urinary flow rates (Qave) and residual urine were determined at baseline and again at 6 weeks as efficacy parameters. The primary parameters used for safety evaluation were vital signs (blood pressure and heart rate) and adverse events. The number of patients with a clinically significant response to treatment with tamsulosin or doxazosin was determined and defined as those with >20% improvement from the baseline Qmax or >20% decrease in total IPSS. RESULTS: The total IPSS decreased significantly in both the tamsulosin and doxazosin groups compared to baseline. There was a significant difference in the decrease in total IPSS between two groups. Qmax, Qave and residual urine significantly improved only in the tamsulosin group. There were no significant differences in systolic blood pressure, diastolic blood pressure or heart rate profile in the tamsulosin group; however, doxazosin resulted in a significant difference in systolic and diastolic blood pressure. Tamsulosin was well tolerated; only three patients (6%) in the tamsulosin group reported an adverse event (dizziness) while 11 patients (22%) in the doxazosin group reported an adverse event (dizziness), one of whom withdrew from the study. CONCLUSIONS: Tamsulosin was shown to be more effective than doxazosin in the treatment of LUTS due to BPH.