Hepatic antioxidant-sensitive respiration. Effect of ethanol, iron and mitochondrial uncoupling

The addition of the antioxidants (+)-cyanidanol-3, butylated hydroxyanisole and ascorbate to the perfused rat liver resulted in a decrease in the rate of oxygen consumption. This basal antioxidant-sensitive respiration of 110-130nmol X min-1 X (g of liver)-1 represents 5-7% of total respiration. Increased antioxidant-sensitive respiratory rates are found after the infusion of increasing concentrations of ethanol (1.8-72.2mM) or iron (35.5-248.5 microM). This respiratory component exhibits a dependence on ethanol or iron concentration, with maximal rates of 200-255 and 330nmol X min-1 X (g of liver)-1 respectively. After the addition of 100 microM-2,4-dinitriphenol, an antioxidant-sensitive respiratory component of 230nmol X min-1 X (g of liver)-1 is found, which is not observed at lower concentrations of the uncoupler (5-50 microM). The lack of effect of the antioxidants used on mitochondrial respiration [the preceding paper, Videla, Villena, Donoso, Giulivi & Boveris (1984) Biochem. J. 223, 879-883] and on the glycolytic rate of the perfused liver suggests that the basal and chemically induced antioxidant-sensitive respiration observed are related to oxygen required for one-electron transfer reactions associated with the generation of active species of oxygen and lipid peroxidation in the liver cell.