Microsomal activation of fluoranthene to mutagenic metabolites.

The in vitro metabolism of fluoranthene (FA) was assessed by incubating 3-[3H]FA, the synthesis of which is described, with rat hepatic microsomal enzymes. Several metabolites including the FA 2,3-diol, FA 2-3,-quinone, 3-OH-FA, 1-OH-FA, and 8-OH-FA were isolated by high-pressure liquid chromatography and identified by comparison of chromatographic properties and uv-visible spectra with those of synthetic standards. The major metabolite produced over the FA concentration range studied (23-233 microM) was FA 2,3-diol, accounting for 29-43% of the total extractable metabolites. This diol was characterized further by high-resolution mass spectroscopy and H-NMR and determined to be identical in structure to the trans-2,3-dihydroxy-2,3-dihydrofluoranthene. The FA 2,3-diol, syn and anti 2,3-diol-1,10b-epoxides, FA 2,3-quinone, and FA 7,8-diol were all shown to be mutagenic toward Salmonella typhimurium TM677. The FA 1,10b-diol and syn and anti FA 1,10b-diol-2,3-epoxides were not mutagenic. The epoxide hydrolase inhibitor, 3,3,3-trichloropropylene oxide, markedly reduced the mutagenic potency of FA while concurrently inhibiting FA 2,3-diol production but not overall FA metabolism. These results suggests that a major metabolic activation pathway of FA resulting in the production of mutagenic species involves the formation of the FA 2,3-diol and the subsequent oxidation of this diol to a FA 2,3-diol-1,10b-epoxide. Another minor activation pathway with mutagenic endpoints may involve the formation of the 7,8-diol.

General approach to the biological analysis of complex mixtures.

The study of potential health effects of combustion effluents involves identifying the substances present and estimating the probable health hazards of each. Unfortunately, this second step cannot be done by using present techniques. Approximations of health hazards by bacterial and human cell assays are being used to set priorities for further biological studies and to suggest needs for modifications of combustion systems. The assumptions underlying this approximation are discussed, and several examples of combustion effluents are reviewed.

The aza-arenes as mutagens for Salmonella typhimurium.

Several unsubstituted aza-arenes have been found to be more mutagenic to Salmonella typhimurium than their corresponding parent hydrocarbons. In most cases, the activity of these compounds depended on the presence of a post-mitochondrial supernatant for metabolic activation, although acridine was mutagenic only in the absence of such an activating system. An examination of the effect of the metabolizing system's concentration on mutagenicity showed that quinoline, benzo[f]quinoline, and phenanthridine have different optima. In an attempt to uncover active intermediates in aza-arene metabolism, N-oxides of quinoline and phenanthridine were synthesized and found to be non-mutagenic, and coincubation with the epoxide hydrase inhibitor trichloropropylene oxide did not affect the mutagenic activity of quinoline or phenanthridine.

Radiosterilization of rat liver microsome containing postmitochondrial supernatant for mutation assays.

Gamma-irradiation was effectively employed to sterilize rat liver postmitochondrial supernatant (PMS), which is required for the metabolic activation of soots and soot-derived polycyclic aromatic hydrocarbons to mutagens. When a known number of Bacillus subtilis spores were added to the PMS and gamma-irradiated at -80 degrees C, a 2-Mrad dose resulted in a 7.5 log kill of the spores. A dose of 3 Mrads was selected as a sufficient effective sterilizing dose and had no significant effect upon the ability of gamma-irradiated PMS to metabolically activate diesel soot and two diesel soot components, benzo(a)pyrene and fluoranthene to mutagens in a Salmonella typhimurium 8-azaguanine resistance forward mutation assay. Three Mrads of gamma-irradiation also had no effect upon the ability of PMS to activate benzo[a]pyrene to a mutagen for the human lymphoblasts. However, gamma-irradiation did reduce the ability of PMS to activate dimethylnitrosamine to a mutagen for S typhimurium.

Comparison of toxicity and mutagenicity of methylnitrosourea, methylnitronitrosoguanidine and ICR-191 among human lymphoblast lines.

The toxic and mutagenic effects of the alkylating agents methylnitrosourea (MNU) and methylnitronitrosoguanidine (MNNG) and of the frameshift mutagen, ICR-191 were compared among 3 human diploid lymphoblast lines, MIT-2, WI-L2 and GM 130. The MIT-2 and WI-L2 lines were both sensitive to the toxic and mutagenic effects of all 3 agents tested. The WI-L2 line was more sensitive to the toxic effects of MNU and MNNG than the MIT-2 line, while it was somewhat less sensitive to the mutagenic effects of these alkylating agents. The GM 130 line was strikingly resistant to both the toxic and mutagenic effects of the alkylating agents. The order of sensitivity to the toxic effect of ICR-191 was MIT-2 greater than WI-L2 greater than GM 130, while the order of sensitivity to the mutagenic effects of this frameshift mutagen was GM 130 greater than MIT-2 greater than WI-L2. These results point to the importance of accounting possible variations in mutability among individuals when extrapolating from any single mutagenicity assay for human risk assessment.

Comparison of toxicity and mutagenicity of butyl methanesulfonate among human lymphoblast lines.

The toxic and mutagenic effects of butyl methanesulfonate (BMS) were compared among four diploid human lymphoblast lines, MIT-2, WI-L2, MGL8B-2 and GM 130. The toxic and mutagenic effects of 24-h exposure to BMS were similar for the MIT-2, WI-L2 and MGL8B-2 lines, while the GM 130 line was strikingly resistant to the toxic and mutagenic effects of BMS.