Treatment with anabolic steroids increases the activity of the mitochondrial outer carnitine palmitoyltransferase in rat liver and fast-twitch muscle.

Treatment of male rats with the anabolic steroids fluoxymesterone or methylandrostanolone increased the activity of the outer carnitine palmitoyltransferase in liver and fast-twitch muscle mitochondria. This effect was not potentiated by physical exercise and was not observed in heart and slow-twitch muscle mitochondria. Anabolic steroids did not affect the sensitivity of the liver enzyme to inhibition by malonyl-CoA. The data presented herein suggest that androgens may have an important physiological role in the regulation of fatty acid oxidation in liver and fast-twitch muscle mitochondria. In addition, our results are at odds with the notion that (most of) the metabolic effects of anabolic steroids on muscle are only evident when physical training is parallely performed.