Activation of phospholipase A2 by carbon tetrachloride in isolated rat hepatocytes

Freshly isolated rat hepatocytes were exposed to carbon tetrachloride (CCl4) for periods up to 4 hr. Phospholipase A2 activity of these preparations was determined by measuring either the release of [3H]arachidonic acid from cellular phospholipids prelabeled with [3H]arachidonic acid or by measuring the formation of [14C]lysophosphatidylethanolamine from cellular lipids prelabeled with [14C]ethanolamine. Through the use of hexane-partition extraction and thin-layer chromatographic analysis of hepatocyte lipid extracts it was found that CCl4 stimulated phospholipase A2 activity in a dose- and time-dependent manner. Carbon tetrachloride at concentrations of 0.23 to 1.3 mM produced a 1.4- to 5.3-fold increase in phospholipase activity which was initiated within 30-60 min of incubation at 37 degrees. The role of phospholipase activation as a secondary mechanism of CCl4-induced hepatocyte injury is discussed.