Abstract

Testosterone has an anabolic effect on skeletal muscle, the mechanisms for which have not been well understood. We hypothesized that testosterone suppresses the synthesis of myostatin, a potent negative regulator of muscular growth. To test this hypothesis, we measured the content of myostatin in muscle after injection of testosterone at varied doses. Male C57BL/6j mice (age, 11 wk; n= 6 for each group) were subjected to the subcutaneous injection of testosterone (0.3, 0.6, or 1.2mg/day per 100g body weight) for 3 days. At the 4th day, the gastrocnemius/ plantaris complex (Gast/ Plant) and the soleus muscles were dissected and the content of myostatin protein was measured. Injection of testosterone tended to cause increases in body weight, Gast/ Plant and soleus muscle wet weight when compared to the control group. Myostatin content in the Gast/ Plant muscle decreased significantly after injection at 1.2mg per 100g body weight as compared to both control and after injection at 0.3mg per 100g body weight. In the soleus muscle, the myostatin content also decreased significantly after injection at 0.3, 0.6 or 1.2mg per 100g body weight when compared to the control group. These results suggest that anabolic effect of testosterone involves decreased production of myostatin within muscle. Verf.-Referat