[Glucocorticoids in intracellular catabolism of myosin and actin].

The catabolic effect of glucocorticoids on the structural proteins of contractile apparatus seems to be realized through the increased alkaline proteinase activity and accelerated synthesis of light enzyme subunits. The administration of large amounts of glucocorticoids increased the excretion of 3-methylhistidine in rats by 60%. Digestion of isolated myofibrils with alkaline proteinase resulted in the degradation of myosin heavy chain and actin. The turnover rate of actin and myosin heavy chain was decreased.