Androgen locally regulates rat bulbocavernosus and levator ani size.

Adult male rats were gonadectomized, and small Silastic capsules filled with hormone were sutured to each bulbocavernosus and levator ani muscle complex (BC/LA). In the first experiment, one capsule contained testosterone (T), while the capsule on the contralateral muscles contained the antiandrogen hydroxyflutamide (hFl). The intent of this treatment was to provide a focus of androgenic stimulation to the muscles on one side. After 30 days, animals were sacrificed, and the BC/LA muscle pairs were removed, weighed, and compared. BC/LAs receiving T treatment were heavier than those receiving hFl treatment (p less than 0.0001), with an average weight difference of 12%. Muscle fibers from T-treated BCs were significantly larger in diameter than those from contralateral, hFl-treated BCs. These results indicate that androgen exerts its anabolic effect by acting locally upon a cell population within or near the BC/LA. When hFl and blank capsules were implanted in castrated males, the hFl-treated muscles were significantly heavier (by 9%), demonstrating an anabolic effect of hFl in the absence of androgen, and refuting the idea that hFl may have caused local toxic effects in the first experiment. Gonadectomized animals given T versus blank capsules had T-treated muscles that were 8% heavier than the blank-treated side. Muscle weights were also compared in animals receiving bilateral denervation of the BC/LA at the time of T and hFl capsule implantation and gonadectomy; local testosterone treatment failed to affect BC/LA weights in these denervated muscles.