Induction of microsomal stearoyl-CoA desaturation by the administration of various peroxisome proliferators.

Male rats were fed a diet containing 0.5% p-chlorophenoxyisobutyric acid (clofibric acid), 1% acetylsalicylic acid, 2% di-(2-ethylhexyl)phthalate, 2% dibutylphthalate, 2% di-(2-ethylhexyl)adipate or 0.5% 4,4'-(isopropylidenedithio)bis(2,6-di-tert-butylphenol)) (probucol) for 7 days. Activity of microsomal stearoyl-CoA desaturation in rat liver was increased, ranging from 2.1 to 3.6 times, in association with an increase in the activity of peroxisomal beta-oxidation and catalase following the administration of clofibric acid, di-(2-ethylhexyl)phthalate, dibutylphthalate or di-(2-ethylhexyl)adipate. The increase in the activity of stearoyl-CoA desaturation by peroxisome proliferators appears to be due to an increase in activity only of the terminal desaturase, but not to changes in either NADH-cytochrome b5 reductase activity or cytochrome b5 content. Unlike peroxisome proliferators, probucol increased little the activity of either microsomal desaturation or peroxisomal beta-oxidation. The percentage of octadecenoic acid in total fatty acid of hepatic microsomes, homogenates and serum was increased markedly by the administration of peroxisome proliferators.