Acid proteolytic activities in mouse liver and muscle tissues after treatment with protease inhibitor leupeptin

Abstract

1. The activities of acid proteolytic enzymes were assayed in the liver and muscular tissues of mice (Mus musculus) 1, 6 and 24 hr after the administration of a protease inhibitor leupeptin (i.p., 15.5 mg/kg body wt). 2. Leupeptin administration induced a strong inhibition of cathepsin B and a moderate inhibition of cathepsin C and acid autolytic rate in mouse liver 1 hr after injection. Thereafter the inhibition reduced and disappeared during 24 hr. 3. The activity of cathepsin D was increased in liver 6 and 24 hr after injection. The activity of β-glueuronidase was not affected by the leupeptin treatment. 4. The administration of leupeptin did not affect the rate of acid autolysis and the activities of cathepsin C and D in cardiac and skeletal muscles. A slight increase in cathepsin B activity was observed 1 hr after leupeptin treatment in calf muscles. 5. The cause of both tissue and enzyme specific changes after leupeptin treatment is discussed.