Differential lipid deacylation during brain ischemia in a homeotherm and a poikilotherm. Content and composition of free fatty acids and triacylglycerols.

The free fatty acid (FFA) and triacylglycerol content and composition are compared in the mouse and toad brain during ischemia. Mouse brain FFA are rapidly increased after decapitation, the maximal production rates being attained within the first minutes. Free arachidonic and stearic acids undergo the highest increases, followed by palmitic, oleic and docosahexaenoic. In contrast, toad brain FFA only changes significantly several hours after decapitation. Triacylglycerols remain virtually unmodified in the amphibian brain during ischemia, whereas in the mammal they are partially decreased, reaching a nearly steady level at about 10 min. This triglyceride breakdown may represent a part, but cannot account for all the changes taking place in FFA. Uneven contributions to the FFA are shown for their counterparts in triacylglycerols. Although the neutral glycerides could be the source of free palmitic acid, they are not responsible for the increases in arachidonic and stearic acids. It is suggested that FFA mainly arise from polar lipid deacylation and a relationship is suggested between the slowness of FFA changes and the higher resistance of poikilotherms to oxygen deprivation.