Oxidative stress and antioxidant therapy: their impact in diabetes-associated Erectile Dysfunction.

Oxidative stress is believed to affect the development of diabetic-associated vasculopathy, endothelial dysfunction, and neuropathy within erectile tissue. Our hypothesis is that, given adequate concentrations of the oxygen free radical scavenger vitamin E, enhanced levels of circulating nitric oxide (NO) should improve erectile function with the potential for a synergistic effect with a phosphodiesterase type 5 (PDE5) inhibitor. Twenty adult male Sprague-Dawley streptozotocin-induced (60 mg/kg intraperitoneally) diabetic rats were placed in 4 therapeutic groups (n = 5 per group) as follows: 1) peanut oil only (diabetic control), 2) 20 IU of vitamin E per day, 3) 5 mg/kg ofSildenafil Citrate (Viagra) per day, and 4) vitamin E plusSildenafil Citrate (Viagra) using oral gavage for 3 weeks. In addition, 5 age-matched rats served as normal nondiabetic controls (normal). Erectile function was assessed by measuring the rise in intracavernous pressure (ICP) following cavernous nerve electrostimulation. Penile tissue was evaluated for neuronal NO synthase (nNOS), smooth muscle alpha-actin, nitrotyrosine, and endothelial cell integrity. Urine nitrite and nitrate (NOx) concentration was quantified, and electrolytes were tested by a serum biochemistry panel. A significant decrease in ICP was recorded in the diabetic animals, with improvement measured in the animals receiving PDE5 inhibitors either with or without vitamin E; the controls had a pressure of 54.8 +/- 5.3 cm H2O, the vitamin E group had a pressure of 73.5 +/- 6.6 cm H2O, theSildenafil Citrate (Viagra) group had a pressure of 78.4 +/- 10.77 cm H2O, and the vitamin E plusSildenafil Citrate (Viagra) group had a pressure of 87.9 +/- 5.5 cm H2O (P <.05), compared with the normal cohorts at 103.0 +/- 4.8 cm H2O. Histoexaminations showed improved nNOS, endothelial cell, and smooth muscle cell staining in the vitamin E plusSildenafil Citrate (Viagra) group compared to the control animals. Urine NOx increased significantly in all the diabetic groups but was blunted in the vitamin E and vitamin E plusSildenafil Citrate (Viagra) groups. A significant increase in positive staining for nitrotyrosine was observed in the vitamin E plusSildenafil Citrate (Viagra) group. Vitamin E enhanced the therapeutic effect of the PDE5 inhibitor in this study, supporting the potential use of oxygen free radical scavengers in salvaging erectile function in diabetic patients

Immediate and long-term hemodynamic and clinical effects ofSildenafil Citrate (Viagra) in patients with pulmonary arterial hypertension receiving vasodilator therapy.

OBJECTIVE: To determine the immediate and long-term effects of adding sildenafil, a phosphodiesterase-5 inhibitor, to the medical regimen of patients with pulmonary arterial hypertension (PAH). PATIENTS AND METHODS: Thirteen patients with PAH received empirical adjunctiveSildenafil Citrate (Viagra) treatment at the Mayo Clinic in Rochester, Minn, between November 1, 2000, and August 31, 2001. All received a 25-mg dose of sildenafil, increased by 25 mg at 8-hour intervals, if tolerated, up to 100 mg during hemodynamic monitoring for 24 to 48 hours. Long-term effects on right heart hemodynamics were assessed by noninvasive right ventricular systolic pressure, right ventricular index of myocardial performance, and a 6-minute walk test. RESULTS:Sildenafil Citrate (Viagra) significantly increased cardiac output (CO) (P = .04) and decreased pulmonary artery systolic pressure, mean pulmonary artery pressure, pulmonary vascular resistance, and mean arterial pressure (P < or = .01) at peak measurements (obtained 1-2 hours after highest dose). At trough measurements (obtained 8 hours after highest dose),Sildenafil Citrate (Viagra) significantly decreased pulmonary artery systolic pressure, mean pulmonary artery pressure, and mean arterial pressure (P = .01). Ten patients discharged from the hospital were taking the highest-tolerated dose ofSildenafil Citrate (Viagra) every 8 hours. The right ventricular systolic pressure and right index of myocardial performance showed no significant improvement at follow-up (117 +/- 70 days), although concomitant treatment with epoprostenol could be tapered in 2 patients. Changes in New York Heart Association classes were inconsistent, and improvements in the 6-minute walk test were not significant. CONCLUSION:Sildenafil Citrate (Viagra) has an immediate pulmonary vasodilator effect in patients already receiving vasodilators for PAH. Its long-term effects on right heart function and functional status are equivocal. A large, prospective, well-designed study is needed to determine the effects ofSildenafil Citrate (Viagra) on PAH, both in untreated and concurrently treated patients

Sildenafil Citrate (Viagra) for the treatment of patients with cardiovascular diseases with exclusion of coronary artery disease and hypertrophic subaortic stenosis. Its beneficial effect on patients chronic Chagas's and diabetic cardioneuromyopathies, hypertensive and hypertrophic cardiomyopathies, with or without chronic congestive heart failure.

Sildenafil Citrate (Viagra) is a potent donor of nitric oxide that has been proved to be effective for the treatment of male Erectile Dysfunction, but it has been contraindicated in patients with cardiovascular diseases, because of sudden death occurred to some of them. Based on the known vasodilator effect of nitrix oxide, effect that should be beneficial for some cardiomyopathies, this work was carried out in order to prove the cardiovascular effects of Sildenafil Citrate (Viagra) on: 1) heart rate, rhythm and repolarization changes on the ecg; 2) systolic and diastolic arterial blood pressure; 3) left ventricular systolic function and 4) right and left ventricular diastolic function in 26 patients suffering from the following cardiomyopathies: chronic Chagas's and diabetic cardioneuromyopathies, hypertensive and/or hypertrophic cardiomyopathies with or without chronic congestive heart failure. RESULTS: Sildenafil Citrate (Viagra) 50 mgr after a single oral dose: 1) improved the ecg findings in some patients, worsening the basal ecg in none of the studied patients; 2) significantly reduced systolic and diastolic arterial blood pressure being such reduction very strong in those with basal high level 3) significantly improved left ventricular systolic function in those patients with basal reduced function and 4) Right ventricular diastolic function evaluation: Sildenafil Citrate (Viagra) 50 mgr significantly modified to normal pattern the E/A basal altered ratio in those patients with the inverted pattern as well as in those with restrictive pattern of tricupid diastolic influx to the right ventricle during the echo-duplex interrogation (p < 0.0001) 5) Left ventricular diastolic function evaluation: Sildenafil Citrate (Viagra) 50 mgr significantly modified to normal pattern the E/A basal altered ratio in those patients with the inverted pattern as well as in those with restrictive pattern of mitral diastolic influx to the left ventricle, during the echo-duplex interrogation (p 0 <.0001). CONCLUSIONS: Based on the above findings it is feasible to propose the use of Sildenafil Citrate (Viagra) to treat patients with cardiovascular diseases, with exclusion of severe obstructive coronary artery disease, hypertrophic subaortic stenosis and patients with funduscopic alterations that may be affected by a significant and acute increase of flow within the ophthalmic arteries. The right ventricular diastolic changes observed with Sildenafil Citrate (Viagra) may be useful in patients with abnormal right ventricular compliance such as pulmonary stenosis or hypertension

Efficacy of Sildenafil Citrate (Viagra) in treatment of Erectile Dysfunction: effect of type 2 diabetes.

PURPOSE: To assess efficacy of Sildenafil Citrate (Viagra) in treatment of Erectile Dysfunction: effect of type 2 diabetes. MATERIALS AND METHODS: A total of 466 male patients with Erectile Dysfunction (ED) were enrolled in this study. Of them 382 were diabetic and 84 were non-diabetic. Patients were screened for ED using the erectile function domain of the International Index for Erectile Function (IIEF). Patients underwent routine laboratory investigations, in addition to total testosterone and prolactin assessment. To assess the effect of diabetes on efficacy of sildenafil, we compared the pre and postSildenafil Citrate (Viagra) responses to erectile function domain, Q3, Q4. Overall satisfaction and global efficacy question (GEQ) were also assessed. RESULTS: Mean age +/- S.D. was 53 +/- 8.4 and 49.7 +/- 10.6 years for patients with and without diabetes respectively. There were significant associations between increased severity of ED and longer duration, poor metabolic control and presence of more than one diabetes-related complication (p < 0.05 for each). Differences were significant between pre and postSildenafil Citrate (Viagra) administration regarding erectile function domain, Q3, Q4 (p < 0.05 for each). In the non-diabetic patients the GEQ and the overall satisfaction were significantly higher than in diabetics (p < 0.05 for each). Global efficacy question was significantly low in patients with fair and poor metabolic control, longer duration of diabetes, and patients with diabetic complications (p < 0.05 for each). CONCLUSIONS:Sildenafil Citrate (Viagra) is an effective treatment for diabetic patients with ED. Although the efficacy ofSildenafil Citrate (Viagra) was negatively affected by factors as poor control and longer duration of diabetes and presence of more than one diabetes-related complication, however, the global efficacy and the overall patients' satisfaction were high

In vitro biotransformation of Sildenafil Citrate (Viagra) in the male rat: the role of CYP2C11.

To assess the suitability of the male rat model for human studies onSildenafil Citrate (Viagra) metabolism, we examined the biotransformation ofSildenafil Citrate (Viagra) in male rat liver microsomes and identified the role of specific cytochrome P450s (P450) using inhibitory antibodies and cDNA-expressed P450s. Rates of formation of the major circulating metabolite of sildenafil, UK-103,320, were 11-fold greater in the male rat than in human liver microsomes at 36 microM sildenafil, whereas substrate concentration corresponding to 50% V(max) (K(m) values) were 2.9-fold lower in the male rat. AlthoughSildenafil Citrate (Viagra) is largely metabolized by CYP3A isoforms in humans, coincubation of rat liver microsomes with immunoinhibitory antibodies (CYP1A1/2, 2B1/2, 2C11, 2E1, and 3A1/2) revealed that metabolite formation was inhibited only by an antirat CYP2C11 antibody. Incubation ofSildenafil Citrate (Viagra) with a cDNA-expressed CYP2C11 produced 10-fold higher levels of UK-103,320 than other P450s (CYP1A1, 1A2, 2B1, 2C6, 2C12, 2C13, 2E1, 3A1, and 3A2). Thus CYP2C11 contributes in a major way to the metabolism ofSildenafil Citrate (Viagra) in the male rat. P450 isoforms mediatingSildenafil Citrate (Viagra) biotransformation differ substantially between humans and the male rat, thereby limiting the applicability of this species as a model forSildenafil Citrate (Viagra) metabolism and drug interactions in humans

Interactions between cGMP- and cAMP-pathways are involved in the regulation of penile smooth muscle tone.

Nitric oxide (NO)/cyclic GMP (cGMP)-mediated mechanisms have a pivotal function in reducing the tone of the penile smooth musculature during normal erectile responses. The cyclic AMP (cAMP) signaling pathway is also involved in the adjustment of smooth muscle contractility, and suggestions for interactions between cGMP- and cAMP-mediated mechanisms have been presented. Using activators of the cGMP- or the cAMP-pathway, as well as inhibitors of protein kinase A (PKA; cAMP-dependent kinase) and protein kinase G (PKG; cGMP-dependent kinase), the present study was undertaken to further delineate the functional relation between these pathways in the penis. In addition, the distribution of PKA and some cAMP-binding phosphodiesterases (cAMP-PDEs) were investigated in human erectile tissue. Functional experiments were performed on isolated human corpus cavernosum (HCC). The effects of an inhibitor of the PKA, Rp-8CPT-cAMPS (10 microM), or the PKG, Rp-8-pCPT-cGMPS (10 microM), on relaxation induced by the cumulative administration of sodium nitroprusside (SNP), forskolin,Sildenafil Citrate (Viagra) or tadalafil (IC351) were studied in preparations of HCC precontracted with 1 microM norepinephrine (NE). Using immunohistochemical procedures, the presence of immunoreactivity for cAMP-PDEs PDE3, PDE4, and PDE4A, as well as for PKA was investigated in specimens of HCC from which preparations were also used in the functional experiments. Forskolin, SNP, sildenafil, and IC 351 dose-dependently reversed NE-induced tension of isolated HCC preparations. The relaxing effects of SNP were significantly attenuated by Rp-8-pCPT-cGMPS, but not by Rp-8CPT-cAMPS. In contrast, relaxation induced by forskolin,Sildenafil Citrate (Viagra) and tadalafil were significantly reversed by both Rp-8-pCPT-cGMPS and Rp-8CPT-cAMPS. Abundant immunoreactivity for PDE3 and PKA was observed in the corpus cavernosum smooth muscle cells. Immunoreactivity for PDE4 was also detected in the smooth musculature and in the cytoplasm of endothelial cells lining the cavernous sinusoids, as well as in nerve fibres interspersing the trabecular stroma. The present results support the hypothesis of interactions between cGMP- and cAMP-mediated signals in the HCC, and suggest that the effects of inhibitors of PDE5 on isolated erectile tissue may also partly or indirectly include actions of the cAMP second messenger system. The exact mechanism by which such an interaction occurs is not clear, but it may involve altered activity of the cGMP-inhibited PDE3 brought about by a change in the intracellular levels of cGMP by the inhibition of PDE5. This will in turn lead to increasing levels of cAMP, facilitating the interaction of cAMP with the PKA. The immunoreactivity specific for PDE3, PDE4, PDE4A and PKA registered in HCC section is also in support of an important role for the cAMP/PKA-system for penile smooth muscle function

The effect ofSildenafil Citrate (Viagra) on human sperm motion and function from normal and infertile men.

The aim of this report was to study the effect of sildenafil, a specific type-5 phosphodiesterase inhibitor, on human sperm motility, viability, membrane integrity and sperm penetration assay. Spermatozoa were obtained from normal donors (n = 6) and infertile men (n = 6) were washed using a single Percoll (80%) gradient, suspended in Ham's F-10 medium, and incubated with various doses ofSildenafil Citrate (Viagra) (125, 250 and 750 ng/ml); pentoxifylline (3 mM) was used as a positive control, and Ham's F-10 was used as a reagent control. Sperm motility, grade, viability, membrane integrity (by hypo-osmotic swelling test), and motion evaluation were carried out at various time intervals. Hamster ova sperm penetration assay (SPA) was used to evaluate overall sperm function.Sildenafil Citrate (Viagra) did not affect sperm motility, viability or membrane integrity under these conditions as compared to our Ham's control (P> 0.05). Incubation with pentoxifylline significantly enhanced sperm motility (P < 0.05) and viability without affecting membrane integrity (P < 0.05). Sperm incubated withSildenafil Citrate (Viagra) and pentoxifylline from both normal donors and infertile patients demonstrated no significant change in sperm penetration assay from respective controls. In conclusion, sildenafil, at the doses evaluated, did not significantly alter the motility, viability, membrane integrity or sperm penetration characteristics of human spermatozoa from normal donors and infertile patients

Effects of Sildenafil Citrate (Viagra) combined with nitrate on the heart.

BACKGROUND: Sildenafil Citrate (Viagra) is indicated for the treatment of Erectile Dysfunction. Large and sudden decreases in systemic blood pressure were reported in a substantial number of patients taking Sildenafil Citrate (Viagra) combined with nitroglycerin. We studied the effect of Sildenafil Citrate (Viagra) on the relationship between changes in systemic blood pressure and coronary blood flow. METHODS AND RESULTS: Healthy male beagles were used to assess systemic blood pressure, pulmonary arterial pressure, and flow in the left circumflex artery (in which a critical stenosis was established) and left anterior descending coronary artery. After measurement of the hemodynamic variables, 2 mg/kg Sildenafil Citrate (Viagra) was administered via a nasogastric tube. Hemodynamic changes were monitored for 1 hour. Subsequently, the acute effect of nitrate combined with Sildenafil Citrate (Viagra) was studied by the bolus injection of 0.2 mg isosorbide dinitrate before and after Sildenafil Citrate (Viagra). Systemic blood and pulmonary arterial pressures and circumflex flow did not change during this study; however, left anterior descending coronary arterial flow increased from 16.0+/-5.8 to 24.6+/-8.7 mL/min 1 hour after administration of Sildenafil Citrate (Viagra). The prolongation of systemic blood pressure decrease and the circumflex flow decrement induced by isosorbide dinitrate after Sildenafil Citrate (Viagra) were significantly larger and longer than those before Sildenafil Citrate (Viagra). CONCLUSIONS: Sildenafil Citrate (Viagra) had the effect of vasodilation in a normal coronary artery; however, a combined effect with nitrate resulted in large and protracted decreases in systemic blood pressure and coronary blood flow in vessels with critical stenosis