No major thermogenic role for (Na+ + K+)-dependent adenosine triphosphatase apparent in hepatocytes from hyperthyroid rats

Abstract

(Na+ + K+)-dependent ATPase activity, heat production and O2 consumption were increased by 59, 62 and 75%, respectively, in hepatocytes from triiodothyronine-treated rats. Ouabain at concentrations of 1 and 10 mM decreased O2 uptake by 2-8% in hepatocytes from euthyroid rats and by 5-15% in hepatocytes from hyperthyroid animals. Heat output was decreased by 4-9% with the glycoside in isolated liver parenchymal cells from the control animals and by 11% in the cells from the triiodothyronine-treated animals. The hypothesis that hepatic (Na+ + K+)-ATPase plays a major role in increased heat production in hepatocytes from hyperthyroid rats is not supported.