Inverter mechanism of the influence exerted by insulin on the plasma membranes of cardiac myocytes in rats of different age

In the plasma membranes of cardiac myocytes from old rats, Na, K-ATPase activity and phosphatidylinositol levels were lower and cardiolipin levels higher than in those from younger (adult) animals. Insulin injected into adult rats elevated Na, K-ATPase activity and phosphatidylethanolarnine levels and caused a sharp fall in phosphatidylinositol levels. In old rats, insulin had no effect on Na, K-ATPase activity, but lowered phosphatidylethanolamine levels. In experiments with cellular hybrids (cytosol+plasma membranes), cytosol from adult rats activated Na, K-ATPase in both adult and old rats, whereas cytosol from old rats failed to activate the enzyme both in old and in adult rats. Actinomycin D prevented the stimulatory effect of insulin on Na,K-ATPase activity. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 120, N ^o 8, pp. 122–125, August, 1995