EFFECT OF ANABOLIC STEROID ON MUSCLE THYMIDINE AND AMINO ACID UPTAKE AFTER WEIGHT-LIFTING EXERCISE

Abstract

1165 We used a rat model of weight-lifting to examine an effect of anabolic androgenic steriod (AAS) on the serial changes in thymidine and amino acid uptake of skeletal muscle during 14 days after a bout of weight-lifting exercise. Wistar male rats (14-16 week old, n=56) were used and divided into 2 groups (steroid loaded; ST and non-loaded control; NC). Nandrolone decanoate(8.3mg/kg, i.m.) was administered for ST group 1 week before exercise.[3H]thymidine and [14C]leucine labeling were used to determine the serial changes in cellular mitotic activity and the level of amino acid uptake and myosin synthesis. The intensity of the exercise and degree of muscle damages were monitored by serum creatine kinase (CK) activity. Significant CK leakage was observed 30-60 min after exercise both in ST and NC group, and the value was significantly lower in ST group, although total lifting weight was significantly higher in ST group. Peak time of thymidine uptake showed 2 days after exercise both in ST and NC, while, significantly lower value was also shown in ST group. Amino acid uptake increased approximately 30% in ST group even before exercise, and peak time of the uptake clearly shifted to left. Monophasic change in amino acid uptake, with a prominent peak of 1 day after exercise (about 2-hold higher than NC) was observed in ST group, in contrast to the biphasic response in NC group (peak increase was shown in 3 and 10 days after exercise). These results suggest that AAS contributes to a protection of cell membrane for the mechanical damages of the muscle induced by a weight-lifting exercise, and enhances protein metabolism with an acceleration of its cycle in the skeletal muscle.