[Comparative study of the effects of alpha-tocopherol and a synthetic antioxidant on respiration and oxidative phosphorylation in rat liver mitochondria].

In order to decide whether vitamin E action on ubiquinone-dependent enzymatic systems of mitochondria and on ubiquinone metabolism consisting in its antioxidative function, the effects of alpha-tocopherol and the most effective synthetic antioxidant, chlorohydrate 2-ethyl-6-methyl-3-hydroxypyridine, were compared. It was shown that the contents of vitamin E and ubiquinone as well as the activities of succinate- and NADH-ubiquinone reductase, succinate- and NADH-dehydrogenases in liver mitochondria are increased and the levels of ATP, adenine nucleotides and phosphate potential in the livers of vitamin E-deficient rats are elevated 3 hours after alpha-tocopherol injection (5 micrograms per 1 g of body weight). The synthetic antioxidant injected under identical conditions at a dose of 50 micrograms per 1 g of body weight did not change the ubiquinone content or the enzymatic activities, but considerably enhanced the ATP level. The same antioxidant when injected at a dose of 105 micrograms per 1 g of body weight did not significantly affect the parameters under study but decreased the activity of succinate-ubiquinone reductase. Thus, the role of vitamin E in oxidative phosphorylation may not only consist in its antioxidant action and is largely due to the regulation of metabolism and functioning of ubiquinone.