Effects of prior fasting and of glucose availability on fatty-acid-induced increases in oxygen consumption in the rat perfused liver.

The influences of fasting and of perfusate glucose concentration on the effect of fatty acid (oleic) on the oxygen consumption of the rat perfused liver were studied. Fasting had no effect on basal hepatic oxygen consumption or on hepatic fatty acid uptake. In the presence of a high perfusate glucose concentration (11 mM), fed and fasted rat livers displayed similar fatty-acid-induced increases in oxygen uptake. Although a low perfusate glucose concentration (2.5 mM) did not affect the oxygen uptake response to fatty acids in the fed group, the response in the fasted group was substantially reduced. The relevance of these observations to the effect of fasting on catecholamine-stimulated thermogenesis and the potential of the liver as a site of regulatory thermogenesis is discussed.