Effect of chronic ethanol on phospholipase A2- and C-activity in chick embryo brain, heart and liver.

The activities of phospholipase A2 (PLA2) and C (PLC) in subcellulal fractions from chick embryo brain, heart and liver were determined using the substrate 1-palmitoy 1-2-N-(4-nitrobenzo-2-oxa-1, 3-diazole amino caproyl-phsphatidylcholine (NBD-PC), and the effect of chronic ethanol treatment on these activities was evaluated. PLA2 and PLC activities of each fraction were assayed by measuring release of N- (4-nitrobenzo-2-oxa-1, 3-diazole) amino caproic acid (NBD-caproic acid) and of 1-palmitoy 1-2-NBD amino caproyl glycerol (NBD-DG) from exogenous NBD-PC. The microsomal membrane fluidity was estimated from diphenylhexatriene anisotropy (gamma). Cytosolic, mitochondorial, and microsomal subcellular fractions were prepared by differential centrifugation of homogenates of the brain, heart, and liver. Microsomal subcellular fractions from the brain, heart and liver of ethanol treated chick embryo showed significantly higher PLA2 and PLC specific activities than did corresponding fractions from non-treated chick embryo. Mitochondrial subcellular fractions from the brain and heart of ethanol-treated chick embryo also showed significantly higher PLA2 and PLC specific activities than the corresponding control fractions. Microsomal fractions from the brain and heart of ethanol-treated chick embryo decreased significantly the gamma than those of control. These results suggest that the change in the membrane fluidity is an apparent prerequisite for the changes of PLA2 and PLC activities.