Abstract

Previous studies have indicated that adrenergic agents may potentiate the hepatotoxicity of compounds such as CCl4. Methamphetamine is a powerful central nervous system stimulating drug which also possesses significant adrenergic activity, and its effects on CCl4 hepatotoxicity were examined in male ICR mice. Cotreatment of mice with methamphetamine (15 mg/kg i.p.) resulted in a significant increase in the hepatocellular necrosis produced by minimally toxic to moderately toxic doses of CCl4 (0.005-0.02 ml/kg i.p.), as indicated by changes in serum alanine aminotransferase activity and by histopathologic examination. Methamphetamine alone at this dosage was not hepatotoxic. The ability of methamphetamine to potentiate CCl4 hepatotoxicity was dose-related and became statistically significant at methamphetamine doses of 10 mg/kg or greater. Pretreatment of animals with either the selective alpha-1 adrenoreceptor antagonist prazosin (5 mg/kg i.p.) or the selective alpha-2 adrenoreceptor antagonist yohimbine (5 mg/kg i.p.) blocked the methamphetamine potentiation. The increase in CCl4 toxicity produced by methamphetamine was not associated with an increase in hepatic concentrations of either CCl4 or one of its major metabolites, chloroform. The increase in toxicity was associated, however, with increases in the in vivo covalent binding of radiolabeled CCl4 to both hepatic proteins and lipids. The cause of the increased covalent binding was not identified, but did not appear to be related to methamphetamine-induced hepatic glutathione suppression. The results of this study suggest that methamphetamine potentiates CCl4 through an adrenoreceptor-related mechanism that may involve either the increased production or diminished conjugation of the reactive metabolites normally formed during the metabolism of CCl4.