Different mechanisms in testosterone action on glycogen metabolism in rat perineal and skeletal muscles.

Testosterone affects glycogen levels in perineal and skeletal muscles by two distinct mechanisms. Both of them show similar sensitivity to androgens (0.1 mg/rat/day of testosterone being effective) and to antiandrogen administration. However, they differ because of the pattern of glycogen increase (early after the androgen injection in the perineal muscles; slowly and with a linear function of time in the skeletal muscles), and because of the different sensitivities to adrenolectomy, diabetes and hypophysectomy. Also, the biochemical changes induced by testosterone in muscles differ. The rate of sugar uptake and phosphorylation is increased in the perineal muscle only; the rate of glucose incorporation into glycogen is increased in the perineal but depressed in the skeletal muscles. Therefore, in the former case glycogen accumulation depends mainly on increased synthesis; in the latter, it is probably the result of a glycogen sparing effect.