[Structural state of the cardiomyocyte sarcolemma in animals of different ages].

Cardiomyocyte plasmalemma membranes of adult (12 months) and old (24-26 months) rats have been studied. Ageing is accompanied with an essential decrease of the content of the membrane protein SH-groups. We have found an increase in the fraction of strongly immobilized spin-labeled SH-groups, a decrease in that of unsaturated lipids, as well as an increase in that of lysophosphatidylcholine in old rats membranes. The pattern of the response of beta-adrenergic receptors to isoproterenol is changed with age. The mobility of spin probe 5NS in the membranes of old rats is lowered at 22.5 degrees C. However there is no statistically significant age difference in the spin-probe mobility at 37 degrees C. Possible role of lysophosphatidylcholine in the stabilization of membrane lipid "fluidity" at physiological temperatures is suggested.