A simple isotopic assay method for human serum phospholipase A2 activity.

An assay using 2-(1-14C)palmitoyl-labelled dipalmitoyl phosphatidylcholine substrate for the determination of serum phospholipase A2 (PLA2) activity is described and validated. The rapid determination of the enzyme activity is enabled by a simple liquid-liquid partition system to replace the laborious thin-layer chromatography used in earlier studies. The PLA2 activity of human pancreatic juice was used for the optimization of the assay. Interference by serum phospholipids can be avoided by using 10 microliter aliquots of serum in the assay, whereas larger amounts caused a progressive inhibition of the enzyme activity. Virtually no enzyme activity is determined in serum from normal healthy subjects (range from 1.2 to 3.0 IU/l). In acute haemorrhagic pancreatitis the PLA2 activity is markedly elevated (range from 10.7 to 42.0 IU/l). Due to the simple extraction of the reaction products the results can be obtained the same day. Therefore, the assay can conveniently be used for the rapid clinical identification of subjects with acute haemorrhagic pancreatitis.