The effect of rat age on the composition and functional activities of skeletal muscle sarcoplasmic reticulum membrane preparations.

The complex of membranes of which cells are comprised have been considered as likely sites of deterioration underlying the decline on physiologic competence with age. Although this concept is an attractive one on theoreical grounds, few direct experimental data are available on the effect of age on biological membranes. Since the sarcoplasmic reticulum of skeletal muscle has been well characterized and is an easily studied membrane system in regard both to its composition and function, the effect of age on this membrane system was explored. Rats of 1, 2, 3, 6, 12, 24 and 28 months of age were the source of sarcoplasmic reticulum membranes which were characterized by the following measurements: phospholipid/protein weight ratio; phospholipid composition; the activity of the (Ca++ + Mg++) -ATPase and the steady state concentration of its phosphorylated intermediate; the ATP-dependent, oxalatepromoted Ca++ transport activity. Although there were some differences between age groups in these basic parameters of sarcoplasmic reticulum composition and function, the data obtained provide no clear evidence of deterioration of these membranes with age.