Effect of gonadal hormones on the cross-sectional area of pubococcygeus muscle fibers in male rat.

Effects of gonadal hormones on dimorphic striated muscles such as the bulbocavernosus/levator ani complex related to male penile erection have been widely studied. However, the action of these hormones on pelvic nondimorphic muscles is not known. In the present study, the sensitivity of the male rat pubococcygeus muscle (Pcm) to gonadal hormones was studied measuring the cross-sectional area (CSA) of its fibers. For this, two experiments were done: in the first, the effect of castration, and in the second the effect of gonadal hormone administration was analyzed. We found that castration after 6 weeks significantly reduced the average CSA of the fibers of this muscle and that castration after 2 or 6 weeks reduced the percentage of fibers with higher CSAs, but only castration after 6 weeks increased the percentage of fibers with the lowest CSA. In comparison with castrated animals implanted with an empty Silastic capsule, Silastic implants of testosterone propionate or dihydrotestosterone significantly increased the average CSA of Pcm fibers, and the treatment with testosterone propionate, estradiol benzoate, or dihydrotestosterone decreased the percentage of fibers with low CSAs and increased the percentage with larger CSAs. Our results could be considered for therapy in patients with damage of the Pcm, and suffering urinary incontinence or ejaculatory dysfunctions.