Circulatory turnover of pancreatic amylase.

Radiolabeled amylase and unlabeled pancreatic amylase were infused into pigs in order to determine the plasma half-life of the enzyme. Regardless of the parameter measured (radioactivity, enzyme activity or concentration), the plasma removal curves could be resolved into three components when subjected to tracer analysis. The plasma half-life was estimated to be approximately 3 hr. Through the use of a recently developed radioimmunoassay specific for porcine pancreatic amylase, the plasma concentration of amylase was calculated at 2.4 mug/ml. Knowing the plasma concentration and half-life of amylase we determined the circulatory turnover of the enzyme. Over a 2.4-hr period, 9.6 mug of pancreatic amylase/ml of plasma must re-enter the circulation to maintain the enzyme at constant levels.