In vitro Inhibition of Protein Catabolism by Alpha2-Macroglobulin in Plasma from a Patient with Posttraumatic Acute Renal Failure

Abstract

Rapid proteolytic digestion of three subunits of phosphorylase kinase was shown in plasma ultrafiltrates from a patient who was admitted with multiple traumatic injuries, respiratory insufficiency, hemorrhagic shock and acute renal failure. The observed cleavage of phosphorylase kinase may be a consequence of protease-antiprotease imbalance. After an initial determination of 80 mg/dl the alpha₂-macroglobulin values were too low to be detected. Addition of purified alpha₂-macroglobulin to the ultrafiltrates resulted in complete inhibition of phosphorylase kinase digestion in vitro. Aprotinin did not inhibit proteolytic digestion. Daily dialysis did not ameliorate the observed protein catabolism of this patient. These findings may have clinical application in hypercatabolic states, if alpha₂-macroglobulin becomes available in a form suitable for human use.Introduction