Elevation of ubiquinone content by peroxisomal inducers in rat liver during aging

The effect of di(2-ethylhexyl)phthalate (DEHP) on the induction of peroxisomes and the content of ubiquinone in the liver was studied in rats between 25 and 496 days of age. During this period, peroxisomal beta-oxidation of fatty acids was greatly decreased but it could be induced many-fold in all ages. The ubiquinone (UQ) content was increased upon induction 6-fold in the first weeks of life, but the extent of this elevation continuously narrowed and no induction could be observed in the oldest animals, even after prolonged treatment with the plasticizer. In contrast, the treatment decreased the amount of liver cholesterol in all age groups. Treatment with this peroxisomal inducer increased the biosynthesis of UQ while the breakdown rate was found to be unaffected, as the half-life of this lipid was 103 and 106 h in control and treated rats, respectively. These results indicate that treatment with peroxisomal inducers increases the liver UQ content by increasing the rate of biosynthesis and that this effect is not apparent in aged rats.