Studies on the Metabolism of d-Limonene (p-Mentha-1,8-diene): III. Effects of d-Limonene on the Lipids and Drug-Metabolizing Enzymes in Rat Livers

1. After a single oral dose of cMimonene (200-1200 mg/kg) no effects were observed on liver triglyceride, microsomal protein, cytochrome b5, and the drug-metabolizing enzymes. Glycogen content was slightly decreased at doses higher than 800 mg/kg, and cytochrome P-450 and δ-aminolaevulinic acid synthetase activity was slightly increased at 1200 mg/kg. 2. After repeated treatment (400 mg/kg/day) for 30 days, the relative liver weight and hepatic phospholipid content were only slightly increased, and liver and serum cholesterol were decreased 49 and 8%, respectively. Of the phospholipid fatty acids, palmitic, linoleic and arachidonic acids were increased, and stearic acid was decreased. Aminopyrine demethylase and aniline hydroxylase were increased 26 and 22%, respectively, and cytochrome P-450 and b5 were likewise increased 31 and 30%.