Interactions in vitro and in vivo between Human and Porcine Cationic Pancreatic Elastase and Plasma Protease Inhibitors

Trace amounts of porcine pancreatic elastase mixed with porcine serum, or injected intravenously into the pig, were found to be bound mainly to alpha 1- and alpha 2-macroglobulin (90%). Alpha 1-macroglobulin approached saturation with elastase before significant binding to alpha 2-macroglobulin was demonstrable. Human pancreatic cationic elastase showed in human serum preferential binding to alpha 2-macroglobulin, but the elastase was also bound by alpha 1-protease inhibitor and by alpha 1-antichymotrypsin. The porcine elastase-alpha 1 alpha 2-macroglobulin complexes injected intravenously or formed in vivo in the pig were rapidly eliminated from the blood stream following a first order reaction with t 1/2 = 8 min. Porcine alpha 1-protease-inhibitor-bound elastase disappeared considerably more slowly.