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

The effect of di(2-ethylhexyl)phthalate (DEHP) on the induction of peroxiso mes 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 f atty acids was greatly decreased but it could be induced many-fold in all a ges. The ubiquinone (UQ) content was increased upon induction 6-fold in the first weeks of life, but the extent of this elevation continuously narrowe d and no induction could be observed in the oldest animals, even after prol onged treatment with the plasticizer. In contrast, the treatment decreased the amount of liver cholesterol in all age groups. Treatment with this pero xisomal inducer increased the biosynthesis of UQ while the breakdown rate w as 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 tre atment with peroxisomal inducers increases the liver UQ content by increasi ng the rate of biosynthesis and that this effect is not apparent in aged ra ts. (C) 1998 Elsevier Science Ireland Ltd. All rights reserved.