Effects of nandrolone phenylpropionate in the horse: (1) resting animal.

The effects of 7 weekly injections of the anabolic steroid nandrolone phenylpropionate (400 mg) were investigated in 4 healthy, mature geldings. Measurement of body weight, nitrogen retention and plasma urea failed to demonstrate a consistent anabolic effects. Examination of biopsies from the semitendinosus and biceps femoris muscles showed no alteration in water content or glycogen concentration with treatment. Similarly no changes were found in the activities of 6 muscle enzymes. However, a significant increase in the proportion of fast twitch low oxidative fibres of the biceps femoris was observed. The effects of the treatment on a wide range of plasma biochemical constituents were investigated. The occurrence of some components of stallion behaviour in the geldings was taken to reflect a residual androgenic activity in the compound.