Studies on reduced and oxidized coenzyme Q (ubiquinones). II. The determination of oxidation-reduction levels of coenzyme Q in mitochondria, microsomes and plasma by high-performance liquid chromatography.

Abstract Reduced and oxidized coenzyme Q 10 (Q 10 H 2 and Q 10 ) in guinea-pig liver mitochondria were rapidly extracted and determined by high-performance liquid chromatography (HPLC). The percentages of Q 10 H 2 as compared to the total (sum of Q 10 and Q 10 H 2 ) were increased by the addition of respiratory substrates such as succinate, malate and β-hydroxybutyrate (State 4). The levels of Q 10 H 2 in State 4 were increased more extensively with electron-transport inhibitors such as KCN, NaN 3 and antimycin A. These results indicate that the method for determining Q 10 H 2 and Q 10 by HPLC is quite useful for investigation of the physiological function of coenzyme Q in mitochondria and other organelles. The reduced and oxidized coenzyme Q levels of rat liver mitochondria, which contain both coenzyme Q 9 and coenzyme Q 10 , were measured simultaneously. The results suggest that coenzymes Q 9 and Q 10 play a similar role as an electron carriers. The liver microsomes of guinea-pig contained approx. 133 nmol total coenzyme Q 10 per g protein. The Q 10 H 2 levels of microsomes were increased from 46.5 to 67.5 and 64.8% with NADH and NADPH, respectively. The plasma levels of total coenzyme Q were 0.92 μg/ml for man, 0.35 μg/ml for guinea-pig and 0.27 μg/ml for rat. The reduced coenzyme Q were also present in those plasma samples. The levels of reduced coenzyme Q were 51.1, 48.9 and 65.3%, respectively.