Sildenafil Citrate Inhibits Agonist Induced Contractions in Isolated Rat Seminal Vesicles

Phosphodiesterase Inhibitors (PDE Inhibitors) and Male Reproduction

The nonspecific PDE inhibitors, particularly the methylxanthines: caffeine, pentoxifylline (PTX), and theophylline, are known to stimulate sperm motility in vitro and have been used to treat sperm prior to insemination. The in vivo effects are less dramatic. A beneficial effect of caffeine, which is a constituent of some medications, remains controversial. Very high doses of caffeine do have negative effects on fertility endpoints in men and experimental species. The specific PDE5 inhibitors, particularly sildenafil and tadalafil, are prescribed for erectile dysfunction, as well as pulmonary hypertension, lower urinary tract symptoms, and premature ejaculation. PDE5 is expressed throughout the contractile tissues of the male reproductive tract, generally increasing contractility. Some PDE5 inhibitors tend to increase circulating testosterone levels somewhat. For short-term exposure consistent with use prior to intercourse, there appears to be minimal effects on semen quality. Several large, randomized controlled trials (RCTs) in healthy men have not found adverse effects of long-term use of these drugs on semen quality. RCTs in infertile men have demonstrated a modest increase in semen quality. Animal studies at human equivalent doses (HED) have produced similar results in young males, but a study in aging male rats found progressive decreases in epididymal sperm quality accompanied by consistent degeneration of the seminal tubules suggesting that studies in older men might be warranted. A concerning study in mice found lower fertilization rates in males treated with HED of sildenafil and mated the next day to untreated females than for control males. Fertility studies in humans are needed.

Seminal vesicles and diabetic neuropathy: ultrasound evaluation after prolonged treatment with a selective phosphodiesterase-5 inhibitor

We have previously reported that infertile patients with diabetes mellitus (DM) have a particular ultrasound features of the seminal vesicles (SV) characterized by higher fundus-to-body ratio and lower pre- and post-ejaculatory difference in body antero-posterior diameter (APD). Based on these premises the aim of the present study was to investigate possible ultrasound SV changes in infertile patients with DM and diabetic neuropathy (DN), after prolonged administration of tadalafil (TAD) (a specific phosphodiesterase-5 inhibitor). To accomplish this, 20 infertile patients with symptomatic DN and erectile dysfunction were selected and arbitrarily divided into two groups which were assigned to: daily administration of 5 mg TAD for 3 months (Group A) (n = 10) and administration of placebo (Group B) (n = 10). All patients underwent to scrotal and prostate-vesicular transrectal ultrasound evaluation and semen analysis (Laboratory Manual for the Examination and Processing of Human Semen, WHO, 2010) before and after treatment. The following SV US parameters were recorded: (i) body APD; (ii) fundus APD; (iii) parietal thickness of the right and left SVs; and (iv) number of polycyclic areas within both SVs. We then calculated the following parameters: (i) fundus/body (F/B) ratio; (ii) difference of the parietal thickness between the right and the left SV and (iii) pre- and post-ejaculatory APD difference. In addition, we also evaluated the SV ejection fraction. Group A patients showed a significant reduction in F/B ratio and higher pre- and post-ejaculatory body SV APD difference compared with baseline or Group B after 3 months. These patients showed also a significant increase in SV ejection fraction and a significant improvement of the total sperm count, progressive motility, seminal levels of fructose, leucocytes and ejaculate volume. In conclusion, these results suggest that infertile DM patients with DN and erectile dysfunction had an improvement of ultrasound features suggestive of diabetic neuropathy after daily treatment with low doses of TAD.

A novel method of seminal vesicle preparation in isolated seminal vesicle experiments in the rat: ring preparation

In this study, we evaluated the efficacy of a novel method of seminal vesicle (SV) preparation-ring preparation method-in isolated SV experiments in the rat. Rat SVs were prepared as strips and rings and applied to organ baths. The relaxation responses by sodium nitroprusside or doxazosin and contractile responses by electrical field stimulation (EFS) were recorded in both groups. We compared the proportion of tissues that showed consistent responses to the stimuli-drug or EFS-in both groups. And magnitudes of the contractile or relaxation responses were also evaluated in the two groups. In strip preparations (n=20), six tissues (30%) showed stable responses to drugs and were regarded to be useful. However, in ring preparations (n=20), 13 tissues (65%) showed stable responses (P<0.001). Similarly, consistent contractile responses to the EFS were recorded in eight strips (40%) and 13 rings (65%) (n=20 in each group; P<0.05). The magnitudes of the relaxations by drugs were not different between the two methods (P=0.42) and the contractions by EFS were higher in ring preparations (P<0.05). The ring preparation seems to be better for responses to drugs and EFS compared with the strip preparations and, therefore, might be an alternative technique for in vitro SV experiments.