Age-related changes in rat liver plasma membrane sphingomyelinase activity.

The age-induced changes of some phospholipid fractions, membrane fluidity and neutral membrane-bound sphingomyelinase (EC 3.1.4.12) activity in rat liver plasma membranes have been investigated. Alterations in the percentage participation of phosphatidylcholine and sphingomyelin with aging have been established. Regression analysis indicated a positive linear correlation (r = 0.927) between the membrane-bound neutral sphingomyelinase activity and the phosphatidylcholine percent in the total plasma membrane phospholipids, as well as a negative linear correlation (r = -0.937) between the enzyme activity and the sphingomyelin/phosphatidylcholine ratio.