RESUMEN
This part of the study is complementary to the previous two studies to complete the risk assessment of the long-term administration of sildenafil on male reproductive system. The study aimed at assessing the effect of the frequency of administration of sildenafil on the hormonal profile in serum of male albino rats to help interpret the morphological alterations in the testis and epididymis exhibited on the previous studies. The effect on sperm count and motility percentage as well as on male reproductive organs weight is to be evaluated. In addition, estimation of nitric oxide [NO] in testicular homogenates is to be performed to reveal on of the various mechanisms of these alterations. Forty-eight male Wistar albino rats were used; and were classified into: Group [1]: [n= 12] negative control group. Group [2]: [n= 36] rats received sildenafil citrate by gavage in a dose of 0.008 mg/g rat. This group was subdivided into 3 subgroups: Subgroup [a]: [n= 12] rats received the dose daily. Subgroup [b]: [n 12] rats received the dose day after day. Subgroup [c]: [n= 12] rats received the dose once per week. The study extended for 18 weeks. The following were estimated: [1] Estimation of serum testosterone, follicle stimulating hormone [FSH] and luteinizing hormone [LH]; [2] Determination of [NO] concentrations in testicular homogenates; [3] Evaluation of sperm count and motility%; [4] Estimation of reproductive organs weight alterations. Alterations in the aforementioned parameters were directly related to the frequency of administration of sildenafil citrate. There were significant reduction in the weights of the testis and epididymis, decrease in serum testosterone, diminution of sperm count and motility%, as well as, increase in [NO] concentrations in testicular homogenates of rats which received the dose daily and day after day