Studies on Serum Amylase in Normal Man and in Acute Pancreatitis

Abstract

Amylase isoenzymes in serum, urine, saliva, jejunal juice and pancreatic tissue were separated by isoelectric focusing. Isoamylase patterns obtained indicated that the majority of amylase activity in normal serum was of salivary gland origin. Pancreatic amylase was characteristically predominant in acute pancreatitis. The increased renal clearance of amylase in acute pancreatitis may be partly due to the increased proportion of the smaller molecular weight pancreatic amylase. A demonstrated increase in the renal clearance of salivary amylase in acute pancreatitis suggested a renal cause also. Autopsy pancreas samples devoid of TAME (p-tosyl arginine methyl ester) esterase activity (e.g., trypsin and plasma enzymes such as thrombin and plasmin) had isoenzyme patterns different to those samples with free proteolytic activity. Incubation of TAME esterase free pancreas with trypsin caused conversion of the former isoamylase pattern to one with the predominant isoenzymes focusing coincident with the predominant peak in serum from acute pancreatitis, jejunal aspirate and TAME esterase positive autopsy pancreas. Such conversion suggested that pancreatic amylase was synthesized in a form different from that found in the intestinal lumen and serum.