Species differences in adrenal lipid peroxidation:: Role of α-tocopherol

Previous reports have noted high levels of lipid peroxidation (LP) in vitro in a variety of adrenocortical preparations. However, we have observed that susceptibility to adrenal LP seems to vary considerably from species to species. The current study was done to confirm these apparent species differences in adrenal LP in vitro and to determine if they were attributable to differences in α-tocopherol content. Incubation of mitochondrial or microsomal preparations from guinea pig or rabbit adrenal glands with ferrous ion (Fe2+) caused a time-dependent increase in the formation of thiobarbituric acid reactive substances (TBARS) accompanied by depletion of α-tocopherol. By contrast, incubation of adrenal mitochondria or microsomes from rats or monkeys with Fe2+ had little or no detectable effect on TBARS and basal adrenal α-tocopherol levels were five to ten-fold greater than those in guinea pigs or rabbits. In addition, there was little change in α-tocopherol concentrations during incubation of rat or monkey adrenal tissue. Dietary α-tocopherol deficiency in rats reduced adrenal α-tocopherol to concentrations approximating those in guinea pigs. Incubation with Fe2+ induced high levels of TBARS in adrenal mitochondria and microsomes from the α-tocopherol deficient rats. Conversely, dietary α-tocopherol supplementation in rabbits increased adrenal α-tocopherol levels and prevented Fe2+ induced TBARS formation in mitochondria and microsomes. The results indicate that there are large species differences in adrenal susceptibility to LP in vitro and that these differences are at least partly attributable to species differences in adrenal α-tocopherol concentrations.