Metabolic effects of anabolic steroid on skeletal muscle.

The purposes of this investigation were to examine the effects of anabolic steroid treatment on protein synthesis in skeletal muscle and on steroid receptors. The experiments were conducted with 230 male albino rats maintained on a diet containing 20% protein. Anabolic steroids (methandrostenolone, methylandrostendiole, and Retabolil) were injected in doses of 0.5 mg/kg body weight. The animals were examined at rest and after swimming exercise of 15 min duration. Quadriceps and gastrocnemius muscle were used for analysis in all experiments. Protein synthesis was studied by means of 14C-leucine incorporation. It was found that anabolic steroid treatment resulted in an increased content of skeletal muscle protein: myosin, myofibrillar, and sarcoplasmic fractions. The activity of RNA-polymerase in skeletal muscle nuclei was increased. The results indicated that in skeletal muscle there were androgen receptors which were binding sites for 3H-testosterone and anabolic steroids. A model for the anabolic steroid action on the regulation of protein synthesis in skeletal muscle was proposed.