Insulin action on cardiac glucose transport. Studies on the role of the Na+/K+ pump.
Isolated muscle cells from adult rat heart have been used to study the relationship between myocardial glucose transport and the activity of the Na+/K+ pump. 86Rb+-uptake by cardiac cells was found to be linear up to 2 min with a steady-state reached by 40-60 min, and was used to monitor the activity of the Na+/K+ pump. Ouabain (10(-3) mol/l) inhibited the steady-state uptake of 86Rb+ by more than 90%. Both, the ouabain-sensitive and ouabain-insensitive 86Rb+-uptake by cardiac cells were found to be unaffected by insulin treatment under conditions where a significant stimulation of 3-O-methylglucose transport occurred. 86Rb+-uptake was markedly reduced by the presence of calcium and/or magnesium, but remained unresponsive towards insulin treatment. Inhibition of the Na+/K+ pump activity by ouabain and a concomitant shift in the intracellular Na+ :K+ ratio did not affect basal or insulin stimulated rates of 3-O-methylglucose transport in cardiac myocytes. The data argue against a functional relationship between the myocardial Na+/K+ pump and the glucose transport system.
D000818:Animals; D001693:Biological Transport, Active / Q000187:drug effects; D005947:Glucose / Q000378:metabolism*; D006321:Heart / Q000187:drug effects; D007328:Insulin / Q000494:pharmacology*; D008297:Male; D009206:Myocardium / Q000378:metabolism*; D011188:Potassium / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D012413:Rubidium / Q000378:metabolism; D012964:Sodium / Q000378:metabolism*; D013997:Time Factors
D007328:Insulin; D012964:Sodium; D005947:Glucose; D012413:Rubidium; D011188:Potassium