EFFECT OF ESTROGEN ON DENERVATED MUSCLE

The rate of increase of glucose 6-phosphate dehydrogenase [G6PD] activity in denervated rat extensor digitorum longus muscle shows sexual dimorphism. This phenomenon was further investigated by assessing the effects of ovariectomy, hypophysectomy, hormone replacement therapy [estradiol 17-.alpha., estradiol 17-.beta., 5.alpha.-dihydrotestosterone, .DELTA.4-androstenedione], and treatment with an estrogen antagonist, MER-25 [1-(p-2-diethylaminoethoxyphenyl)-1-phenyl-2-p-methoxyphenyl ethanol]. Physiologic doses of estrogens enhance the rate and extent of the increase in G6PD activity after denervation. Aromatization of androgens may be a significant source of estrogen involved in hormonal modulation of the neural control of G6PD and other processes in muscle. Choline acetyltransferase activity, a marker for the neuromuscular synapse, decreased in rat extensor digitorum longus muscles after denervation, but was unaffected by ovariectomy.