Calorigenic Action of Triiodothyronine on White Fat Cells: Effects of Ouabain, Oligomycin, and Catecholamines

Abstract

In white fat cells obtained from normal rats given 25 micrograms of L-3,5,3’-triiodothyronine (T-3) 18 hours prior to sacrifice, lipolysis was increased and the ATP content decreased by norepinephrine (0.2-0.3 μM) after incubation for either 10 or ISO minutes. Basal ATP content was unaffected by T-3 treatment. In control cells, norepinephrine did not alter ATP levels. The oxygen consumption of white fat cells incubated either in the absence or presence of glucose was increased by T-3 treatment. Oligomycin had little inhibitory effect on basal respiration of fat cells incubated in the presence of glucose but abolished the increase due to T-3 treatment. Ouabain at 0.1 or 1 DIM did not block respiration in fat cells from either control T-3 treated rats under conditions in which it blocked the lipolytic action of catecholamines. The present results suggest that the stimulation of respiration in white fat cells by T-3 is secondary to increased utilization or dissipation of energy conserved during electron transport. (Endocrinology89: 1205, 1971)