Biosynthesis of ubiquinone and ubichromenol in vitamin A-deficient rats

Relaxation of arterial smooth muscle: a new function of a water-soluble degradation product of coenzyme Q (ubiquinone)

Treatment of coenzyme Q with ozone yielded a degradation product having unmodified ring that retained its spectral characteristics and a truncated side-chain that made it water-soluble. This derivative, but not the intact lipid-quinone, showed relaxation of phenylephrine-contracted rat arterial rings. This effect offers an explanation for the known hypotensive action of exogenous coenzyme Q regardless of its side-chain length.

Changes in mitochondrial and microsomal rat liver coenzyme Q9 and Q10 content induced by dietary fat and endogenous lipid peroxidation

The influence of different kinds of dietary fat (8%) and of endogenous lipid peroxidation with regard to coenzyme Q9 (CoQ9) and coenzyme Q10 (CoQ10) concentrations in mitochondria and microsomes from rat liver has been investigated by means of an HPLC technique. Although the different diet fats used did not produce any effect on microsomes, it was possible to show that each experimental diet differently influenced the mitochondrial levels of CoQ9 and CoQ10. The highest mitochondrial CoQ content was found in case of a diet supplemented with corn oil. An endogenous oxidative stress induced by adriamycin was able to produce a sharp decrease in mitochondrial CoQ9 levels in the rats to which corn oil was administered. The results suggest that dietary fat ought to be considered when studies concerning CoQ mitochondrial levels are carried out.

Quinone mediated ATP production in the filarial parasite Setaria digitata

The cattle filarial parasite Setaria digitata, a facultative anaerobe which is reported to be cyanide insensitive, lacks cytochromes and presents many unique characters. Experiments showed the occurrence of two lower quinones Q6 and Q8 and its rapid synthesis is revealed by a [14C] acetate incorporation study. A schematic quinone mediated hydrogen peroxide production with the generation of ATP through oxidation of substrates has been proposed. Search for specific blockers at the level of quinone might prove to be an effective measure for the control of filarial parasites and thereby filariasis.

Effect of alpha-p-chlorophenoxyisobutyrate on the metabolism of isoprenoid compounds in the rat

1. Feeding of alpha-p-chlorophenoxyisobutyrate (CPIB) to rats increased ubiquinone concentration in the liver but not in other tissues. The increase was progressive with the time of feeding and related to the concentration of CPIB in the diet. 2. Incorporation of [1-(14)C]acetate, but not of [2-(14)C]mevalonate, into sterols in the liver in vivo or by liver slices in vitro was decreased on feeding the rats with CPIB. However, incorporation of mevalonate into ubiquinone increased. 3. CPIB, when added in low concentrations to liver slices, had no effect on isoprene synthesis from acetate; higher concentrations, however, were inhibitory. 4. No activation of ubiquinone synthesis from mevalonate was observed when CPIB was added to the liver slices synthesizing ubiquinone. 5. The increase in ubiquinone in CPIB-fed animals appears to be due to increased synthesis in the initial stages and to decreased catabolism in the later stages. 6. An inverse relationship was found between the concentration of ubiquinone in the liver and the serum sterol concentration in CPIB-fed rats.

Metabolism of ubiquinone in relation to thyroxine status

1. Under conditions of thyrotoxicosis induced by feeding rats with iodinated casein, ubiquinone concentration was found to increase in the liver by increased synthesis and by partly decreased catabolism leading to its accumulation. The increased ubiquinone was found primarily in the mitochondrial and supernatant fractions. 2. Supplementing the diet with thyroxine, at less than toxic doses, also increased the synthesis and the concentration of ubiquinone in the liver. 3. In the condition of hypothyroidism obtained by feeding rats with thiouracil the concentration and the synthesis of ubiquinone in the liver showed a small decrease. 4. Synthesis of ubiquinone in liver slices was partially inhibited by addition of thyroxine in vitro. Therefore the activation effect on ubiquinone synthesis of excess of thyroxine in the intact animals appears to be by an indirect mechanism.

Interrelationship of vitamins A and C on tissue ubiquinones and sterols of rats and guinea pigs

The effect of administration of ascorbic acid to normal or vitamin A-deficient rats was studied in relation to hepatic levels of ubiquinones and sterols. Similar studies were made on tissues from guinea pigs deficient in vitamin C, vitamin A, or both. Vitamin A deficiency increased the concentration of liver ubiquinones in the rat. Administration of ascorbate did not influence tissue levels of ubiquinones or sterols. Vitamin C deficiency increased the concentration of sterols but not of ubiquinones in the liver of the guinea pig. Vitamin A deficiency did not increase ubiquinones nor did a combined deficiency of vitamins A and C. A secondary effect of vitamin C deficiency in the vitamin A-deficient rat is not the cause of increased ubiquinone levels.