| Abstract: | The interaction of quinones (menadione and duroquinone) with DT-diaphorase and mitochondrial electron transport chain translocators at low (120 mosM) and high (400 mosM) values of the medium tonicity in the quinone concentration range of 6-90 microM was studied. It was shown that with a rise in menadione (K3) concentration the number of electron transport carriers interacting with it increase. At K3 concentration of 6 microM the latter is reduced by DT-diaphorase and fully oxidized via the Q-cycle. At K3 concentration of 15 microM the latter is also reduced by DT-diaphorase via the Q-cycle, but in this case the oxidation is incomplete (about 30% K3H2 is oxidized by the terminal part of the respiratory chain). At 90 microM K3 50% of quinone is reduced by DT-diaphorase and 50% by the respiratory chain NADH dehydrogenase complex enzymes; about 30% of K3H2 is oxidized via the Q-cycle, about 20%--by the terminal part of the respiratory chain and about 50%--by O2 without cytochrome oxidase. Unlike menadione, duroquinone (6-90 microM) is reduced only by DT-diaphorase and is oxidized in all cases by cytochrome oxidase. It was shown that the increase in the mitochondrial matrix volume in low tonicity media decreases the rate of the DT-diaphorase shunt operation. |
