[Regulation of ubiquinone metabolism: a study in the regenerating rat liver]

Distinct increase in biosynthesis of ubiquinone and sterols was observed in regenerating liver tissue of rats; the rate of ubiquinone degradation was not altered. This phenomenon was characterized by incorporation of 14C-tyrosine into ubiquinone and of I-14C-acetate into ubiquinone and sterols in vivo and in vitro. An increased turnover of enzymes, participating in synthesis of the substances, was found in cytoplasm and mitochondria of regenerating liver after administration into animals with subtotal hepatectomy of specific inhibitors: cycloheximide, ethidium bromide, hydroxytetracycline, cholesterol and cholesterol with bile; relative rates of labelled precursors incorporation into ubiquinone and sterols were then estimated in vitro. The highest rate of I-14C-pacetate incorporation into ubiquinone was found within 24 hrs after hepatectomy, into sterols--within 48 hrs and 72 hrs after hepatectomy. Mitochondrial DNA appear to code certain functional proteins responsible for synthesis of ubiquinone in mitochondria. The enzymes, which formed precursors of isoprenoid substances in cytoplasm, were shown to regulate ubiquinone biosynthesis. Regulation of ubiquinone biosynthesis in regenerating liver is discussed.