Changes in protein synthesis in rats in response to endurance training

Abstract

Experiments were conducted to investigate the influence of endurance exercise training on protein synthesis in skeletal muscle, heart, and liver. Training decreased incorporation of [ 14C]-leucine into proteins of the stromal fraction of muscle but there was no change in amino acid incorporation into proteins of the sarcoplasmic and myofibrillar fractions. Incorporation of [ 14C]-leucine into the protein of heart, liver, and plasma was depressed in trained rats compared to untrained rats. The specific radioactivity of [ 14C]-leucine was similar in tissues of trained and untrained rats and thus the depressed amino acid incorporation represents a decrease in the rate of protein synthesis. These observations demonstrate that the adaptation of muscle protein metabolism to endurance training is quite different than the alterations during work-induced hypertrophy of muscle. The difference in adaptation probably relates to the functional differences between the types of exercise. However depression of protein synthesis in trained rats is a general effect in several tissues and not an effect localized in muscle tissue.