Effect of muscular activity on the turnover rate of actin and myosin heavy and light chains in different types of skeletal muscle.

In endurance-trained rats the myosin HC have a more rapid turnover rate than in control animals in all three types of skeletal muscle fibres, but in sprint-trained rats only in fast-glycolytic and fast-oxidative-glycolytic fibres. A comparison of the actin turnover rate in sprint- and endurance-trained animals shows that in both groups there are more rapid turnover rates in all types of muscle fibres in comparison with control rats. During long-lasting exhaustive exercise the turnover rate of myosin HC decreases. Twelve hours after exercise, myosin LC 2 and 3, and actin have a more rapid turnover than in control rats. Changes in the turnover rate of muscle contractile proteins during exercise and the recovery period after exercise reflect the functional conditions of the contractile apparatus in different types of skeletal muscle fibres and have a physiological significance.