In vivo effect of pancreatic phospholipase A2 on the arachidonic acid cascade

Background. In acute pancreatitis, pancreatic phospholipase A, increases in systemic circulation. Yet the pathophysiological significance is controversial, because previous in vitro studies have shown that the enzyme has little cytotoxicity or ability to activate the arachidonic acid cascade by itself in contrast to other isozymes. Aim of the Study. The aims of this study are to examine the effect of pancreatic phospholipase A(2) on the arachidonic acid cascade in vivo; to explain the discrepancy, if present, between in vitro and in vivo findings; and to reassess the pathophysiological significance of circulating pancreatic phospholipase A(2). Methods. Pancreatic phospholipase A(2) was infused intravenously in guinea pigs, and changes in the arachidonic acid cascade, plasma lipoprotein, and cardiopulmonary function were investigated. Results. Plasma concentrations of 6-keto-prostaglandin F-1alpha, prostaglandin E-2, and thromboxane B-2 increased after intravenous (iv) infusion of pancreatic phospholipase A(2). Some of the plasma phospholipids such as phosphatidylcholine and phosphatidylethanolamine decreased, and free dihomo-gamma-linolenic acid, arachidonic acid, and eicosapentaenoic acid were detected in plasma. These changes were accompanied with decreases in blood pressure, heart rate, and base excess. Conclusion. Circulating pancreatic phospholipase A(2) activates the arachidonic acid cascade, probably by supplying free eicosanoid precursors from plasma lipoprotein to eicosanoid-producing cells. It is supposed to be a cause of systemic complications in acute pancreatitis.