Age-related changes in rat liver plasma membrane phospholipase A2 activity

The alterations of the lipid composition and fluidity of liver plasma membranes as well as the activity of membrane-bound phospholipase A2 (EC 3.1.1.4) in male and female rats of different ages are investigated. An age-induced increase of the protein/phospholipid and cholesterol/phospholipid ratios is observed, as well as a decrease in the unsaturation index of plasma membrane phosphatidylcholine. These changes induce an augmentation of the steady-state fluorescent anisotropy-rs and structural order parameter for 1,6-diphenyl-1,3,5-hexatriene-SDPH in plasma membranes. The membrane-bound phospholipase A2 activity is enhanced with aging, correlating well with the reduced membrane fluidity. The sex-determined alterations in all these parameters is also investigated.