Quinoline: conversion to a mutagen by human and rodent liver

Quinoline, a hepatocarcinogen in rats, and 23 quinoline derivatives were tested for mutagenic activity with the Ames Salmonella typhimurium assay. Quinoline, 5-hydroxyquinoline, and 8-hydroxyquinoline were mutagenic in strain TA 100 when Aroclor 1254-induced rat (male outbred Sprague-Dawley) liver homogenate was present in the incubation mixture. Enzyme preparations from rats pretreated with P-448-dependent aryl hydrocarbon hydroxylase inducers [3-methylcholanthrene (MCA) and beta-naphthoflavone] and MCA-treated "responsive" C57BL mice also metabolized quinoline to a mutagen, but phenobarbital and pregnenolone-16alpha-carbonitrile pretreatment did not yield active preparations. The mutagenicity of quinoline was blocked by the in vitro addition of menadione, butylated hydroxytoluene, alpha-naphthoflavone, vitamin A acetate, and glutathione to the test system. Depletion of glutathione by diethyl maleate pretreatment in vivo enhanced the mutagenic potential of the liver enzyme preparation. Mutagenic activity was correlated to the formation of water-soluble quinoline metabolites, and we suggested that the reactive quinoline intermediate is quinoline-2,3-epoxide. Microsomal enzymes isolated from human liver tissue, but not lung tissue, also converted quinoline to a mutagen.