Improved method for the determination of phospholipase A2 catalytic activity concentration in human serum and ascites.

An improved radiochemical method is presented for the selective determination of phospholipase A2 activity in human serum and ascites, using only commercially available reagents. The method can be applied to large quantities of samples. As substrate we used 1,2-dipalmitoyl-sn-glycero(3)phosphorylcholine and phosphatidylcholine containing tritiated palmitic acid in position 2 (1-palmitoyl,2-[9,10-3H]palmitoyl-sn-glycero(3)phosphorylcholine). The liberated fatty acids are extracted and radioactivity is detected in a liquid scintillation spectrometer. A preliminary reference range of human serum samples was established ranging up to 1.0 U/l. In sera of patients with acute pancreatitis we found activities up to 20 U/l. The correlation of phospholipase A2 activity with that of other enzymes and with the severity and complications of acute pancreatitis was investigated. A possible relationship between phospholipase A2 activities and pulmonary complications is discussed.