Testosterone and muscle hypertrophy in female rats.

The effects of chronic treatment with testosterone propionate on compensatory muscle hypertrophy secondary to synergist removal were studied in female rats. Synergist removal resulted in a significant (2-fold) increase in muscle wet weight, with no changes in protein concentration. As reported previously, oxidation of [2-14C]pyruvate to 14CO2 was significantly decreased in hypertrophic muscles. In addition, malate dehydrogenase and lactate dehydrogenase activities were significantly decreased in overloaded muscles on a wet weight basis but not on the basis of noncollagen protein. These data suggest that specific metabolic adaptations may occur in response to overload of muscle. Administration of testosterone propionate in subcutaneously implanted Silastic capsules resulted in a 20-fold increase in serum testosterone levels. This treatment had no effect on body weight, muscle weight, pyruvate oxidation, or malate and lactate dehydrogenase activities in both control and hypertrophic muscles, although there was an effect on the noncollagen protein content of overloaded muscles. These results do not support the hypothesis that androgens, in conjunction with weight-bearing exercise in female subjects, are effective in increasing muscle mass or function in female subjects.