MODULATION OF NA-PUMP AND NA+(,K+)LI+-EXCHANGE ACTIVITY IN RABBIT ERYTHROCYTES AT DIFFERENT STAGES OF CHOLESTEROL FEEDING/

The activities of the Na+,K+-pump and Na+/Li+-exchange and the intrace llular concentration of Na+ in erythrocytes of rabbits with experiment al hypercholesterolemia were studied at different stages of cholestero l feeding, as well as at different intervals upon discontinuation of t he cholesterol supplementation. After sufficiently long periods of fee ding animals with cholesterol (1.5-2 months), a significant activation of the Na+,K+-pump, reduction of the Na+/Li+-exchange rate, and lower ing of the intracellular sodium content in erythrocytes of rabbits fro m experimental groups were observed. Several months after discontinuat ion of cholesterol feeding there was a partial normalization of the st udied parameters. However, at an initial stage of the experiment (20 d ays after the beginning of cholesterol feeding), as well as 2 weeks af ter cholesterol feeding was discontinued, no changes in the activities of the ion transport systems and in [Na+](i) were observed despite su bstantial changes in the plasma cholesterol level. It is suggested tha t the observed effect of dietary cholesterol on the activity of the io n carriers may be mediated by an effect on the expression of the corre sponding genes.