Dose-dependent effects of an anabolic steroid, nandrolone phenylpropionate (Durabolin), on body composition and muscle protein metabolism in female rats.

The effects of three doses (1, 4 and 10 mg/kg body weight) of an anabolic steroid, nandrolone phenylpropionate (NPP), on body weight and composition, and muscle protein metabolism were investigated in female rats. Daily injections of 1 mg/kg of NPP for 10 days caused a significant increase in weight gain which was associated with an increase in body protein (9%) without affecting body fat. At higher doses this effect on body weight was attenuated, resulting in no change in body weight at 10 mg/kg. However body protein content was still increased (9%) whereas body fat content was significantly reduced (32%). NPP did not affect metabolizable energy intake at any dose tested. Body energy gain and gross energetic efficiency were both significantly reduced in animals treated with a dose of 10 mg/kg. The mass and protein content of gastrocnemius muscle were significantly increased in animals injected with NPP at all doses. Muscle protein synthesis measured in vivo was also significantly stimulated at 1 and 4 mg/kg but was not affected at 10 mg/kg. These data confirm an anabolic action of NPP and suggest highly dose-dependent effects on other parameters such as body weight, fat deposition and muscle protein synthesis.