Androgens enhance in vivo 2-deoxyglucose uptake by rat striated muscle.
Testosterone propionate causes a striking increase in in vivo uptake of 2-deoxyglucose by the levator ani muscle of immature male rats. Autoradiography showed the labeled 2-deoxyglucose to be uniformly distributed over the entire muscle. Liquid scintillation counting of whole muscles allowed quantification of 2-deoxyglucose uptake. After a single sc injection of testosterone propionate, no enhancement of 2-deoxyglucose uptake could be seen before 3.5 h, at which time uptake was increased 2-fold; maximum enhancement (4-fold) was attained at 12 h. 2-Deoxyglucose uptake remained elevated at twice the control value at 72 h. Muscle weight did not increase until sometime after 24 h; by 39 h, it was 50% greater than the control value; by 72 h, wet weight was double the control value. The effect of testosterone propionate probably is mediated by specific androgen receptors, since the administration of either 5 alpha-dihydrotestosterone or fluoxymesterone, potent androgens, caused severalfold increases in 2-deoxyglucose uptake in the levator ani muscle, while administration of 17 beta-estradiol, corticosterone, and etiocholanolone, an inactive metabolite of testosterone, did not. Furthermore, the effect of testosterone propionate was blocked by simultaneous administration of an androgen antagonist, cyproterone acetate. Testosterone propionate also enhanced uptake of 2-deoxyglucose in the bulbocavernosus (253% over control) and extensor digitorum longus muscles (150% over control), but not in the biceps brachii or soleus. Increased glucose uptake may be an important early step in the anabolic response of muscle to androgens.