Cerebral microvessel phospholipase A2 activity in senescent mouse.

Phospholipase A2 activity was measured in cerebral microvessels isolated from 5 to 6 month (young adult) and 21 to 24 month (aged adult) old mice. Radiolabeled 1-stearoyl-2-[1-14C]arachidonyl choline phosphoglyceride was used as the enzyme substrate, and enzyme activity determined at pH 8 and pH 9. Activity in older animals was significantly less than in younger animals at both pH's. With choline phosphoglyceride as a substrate, phospholipase A2 activity was predominantly Ca(2+)-dependent, although a small, but measurable Ca(2+)-independent component was present. Negligible production of diacylglycerol indicated little or no phospholipase C activity. These findings indicate that activity of a phospholipase A2, which utilizes choline phosphoglyceride as a substrate, is affected by the aging process. Moreover, a change in PLA2 activity would result in altered metabolism of specific phosphoglycerides and turnover of fatty acids at the sn-2 position in cerebral microvessels.