Age-dependent alterations in lipids and function of rat heart sarcolemma

The objective of the present study was to examine the effect of age on heart sarcolemma structure and function. Sarcolemmal fractions were prepared from hearts of young (1-1.5 months) and adult (10-12 months) rats and assayed for marker enzyme activities. The membrane fractions were found to be devoid of other cellular organelles upon examination by electron microscopy. They were enriched with 5'-nucleotidase and devoid of succinate dehydrogenase activity. The only age-related lipid compositional changes noted in these membranes were changes in the fatty acid composition of membrane phospholipids with increasing age. Most changes were detected in phosphatidylcholine and phosphatidylethanolamine with very little alteration of sphingomyelin and phosphatidylserine plus phosphatidylinositol fatty acids. Polyunsaturated fatty acids, especially 18:2 and 20:4, were decreased with saturated fatty acids increased in membrane phosphatidylcholine and phosphatidylethanolamine fractions as the animal develops. There was a decrease in the specific activities of (Na+ + K+)-ATPase and 5'-nucleotidase of these membranes with age. On the other hand, membrane (K+)-rho-nitrophenylphosphatase was not affected by age.