Retention of hormonal sensitivity in free grafts of the levator ani muscle.

The regenerating levator ani muscle of the rat is known to retain its sensitivity to the effects of testosterone. To determine whether hormonal sensitivity of the regenerating muscle is purely myogenic or requires some interaction with the pudendal nerve or the local humoral environment, levator ani muscles were freely grafted in place of the soleus or extensor digitorum longus muscles in normal, castrated, or testosterone propionate-treated rats. Grafts into the bed of the soleus were unsatisfactory due to poor reinnervation. Levator ani muscles grafted into the bed of the extensor showed a sensitivity to testosterone as demonstrated by gross wet weight, cross-sectional area of the muscle fibers, and twitch and tetanic tensions, Neither histochemical analysis nor contraction times were useful in distinguishing between hormonal groups. It is concluded that hormonal sensitivity of the regenerating levator ani muscle is principally, if not entirely, myogenic.