Effect of Exercise on Muscle Protein Metabolism during Growth in a Rat

Abstract

The present study vyas performed to determine the effects of daily exercise on muscle protein metabolism during growth of a rat. Twenty male rats (7 weeks of age) of Wistar strain were divided into sedentary (Control) and exercising (Exercise) groups. The rats were studied for 10 weeks. The following main results were obtained : 1) The increase of body weight in the exercise group was significantly lower than that of the control group. However, the wet weight per body weight of the MM. gastrocnemius and soleus in the exercise group tended to be higher when compared to the control group. 2) Urinary excretion of urea-nitrogen in the exercise group maintained constant levels, and that of the control group had decreased at the end of experimental period. The protein intake showed no noticeable difference between the control and the exercise groups. 3) Urinary excretion of 3-methylhistidine in each group decreased gradually and had a tendency to be higher in the exercise group than in the control group throughout the experimental period. 4) The fractional turnover rate of myofibrillar protein in the exercise group tended to higher. Especially in the synthetic rate at the first half of experimental period, the exercise group showed a tendency to be higher than the control group. These observations suggest that during the experimental period protein metabolism activity of the whole body and skeletal muscle are higher in the exercise group than in the control group. It is concluded that skeletal muscle protein metabolism increases by exercise loading during growth.