The effect of muscular exercise on the microsomal enzyme system of the rat liver.

Regular muscular work--in the form of swimming or running--was studied for its effect on hexobarbital sleeping time and on some components of the hepatic monooxygenase system. Sleeping times became shorter after both kinds of exercise. Thus, the causative factor in this type of enzyme induction is regular physical exercise. Antipyrine elimination was also faster in rats exercised by swimming. Regular exertion elicited a rise in the concentration or activity of some components of the hepatic microsomal monooxygenase system (cytochrome P450, cytochrome b5 and NADPH cytochrome reducatase EC 1.6.2.3.). The inducing effect of muscular work appears to be most similar to the phenobarbital type of induction. In the development of this exercise-induced rise of enzymatic activity some as yet unidentified humoral and metabolic changes associated with daily physical training are thought to play a role.