Influence of compensatory overload on glucocorticoid receptors in rat skeletal muscle.

The present study was undertaken to evaluate the state of glucocorticoid cytosol receptor binding in muscle hypertrophied by compensatory overload in normal, testosterone-treated, and castrated male rats. Compensatory hypertrophy in plantaris muscles was induced by myomectomy of the gastrocnemius and the soleus of 100 male Sprague-Dawley rats. The controlateral sham-operated limb was used as control. The rats were divided in 3 groups: control injected with peanut oil, castrated injected with peanut oil, and castrated injected with testosterone propionate (1 mg/rat). Five days later the animals were sacrificed and the muscles obtained for glucocorticoid receptor binding studies using [3H]dexamethasone as ligand. Receptor concentrations (Bmax) were significantly increased in hypertrophied muscle and the increase was not affected either by castration or by androgen treatment. These results tend to suggest that gonadal steroids do not participate in hypertrophy-induced proliferation of glucocorticoid receptors.