Effect of Substituted Aryl Group in Water-soluble Porphyrins on 2-Aminofluorene Activation in Ames Assay

Abstract

Chemical models for cytochrome P450, consisting of an iron porphyrin complex and an oxidant, have been used as substitutes for the S-9 mix for detecting mutagenicity of promutagens in the Ames assay. In this study, we developed optimized procedures for the Ames mutation assay using a water-insoluble 5,10,15,20-tetrakis(pentafluorophenyl)porphyrinatoiron(III) chloride (F₅P) or a water-soluble 5,10,15,20-tetrakis(1-methylpyridinium-4-yl)porphyrinatoiron(III) (4-MPy) plus tert-butyl hydroperoxide (t-BuOOH) as a chemical model to determine 2-aminofluorene (AF) mutagenicity. The model system including the water-insoluble F₅P plus t-BuOOH demonstrated higher AF mutagenicity when the tester strain was added following the incubation period of the reaction mixture. In contrast, in the system including the water-soluble 4-MPy plus t-BuOOH, the activity of AF mutagenicity was highest when the tester strain was added to the reaction mixture prior to incubation. It is thus possible to detect short-lived mutagenic metabolites by the latter procedure. AF mutagenicity was compared among diverse water-soluble iron porphyrins plus t-BuOOH. The results showed that a cationic 4-MPy/t-BuOOH had the highest capacity for mutagenic activation of AF among the chemical models tested.