Enhanced proteolytic activity--cause of protein catabolism in acute renal failure

We demonstrated pH and time dependent proteolytic digestion of bovine serum albumin by sera and of phosphorylase kinase by ultrafiltrates of sera in two of eight patients with hypercatabolic acute renal failure. Phosphorylase kinase was isolated from rabbit skeletal muscle. Ultrafiltrates of sera were prepared by ultrafiltration with an Amicon XM 50 filter. These techniques appear to be sensitive indicators of active proteases in sera of patients with hypercatabolic acute renal failure and may be superior signs of hypercatabolism than serum alpha 2-macroglobulin and alpha 1-antitrypsin. Moreover, these procedures allow one to characterize the protease and to assess, in vitro, the effectiveness of specific inhibitors of these proteases.