Extracellular phospholipase A2 detected at inflamed sites in rats does not originate from platelets

Extracellular phospholipase A2 activity has been detected in caseinate-induced peritoneal fluid in rats. We studied the source of this extracellular phospholipase A2 in 'platelet-poor' rats which had been pretreated with an intravenous injection of rabbit anti-rat platelet serum. In these rats, the increase in the peritoneal fluid extracellular phospholipase A2 level at the inflamed sites was almost identical to that observed in control rats, although platelet numbers in peripheral blood were decreased markedly. This observation suggests that extracellular phospholipase A2 in the peritoneal cavity is not derived mainly from platelets.