Metabolic activation of carcinogens in the salmonella mutagenicity assay by hamster and rat liver S‐9 preparations

Abstract

Before exerting a carcinogenic o r mutagenic effect, many carcinogens must undergo metabolic activation. Liver S-9 preparations from rats treated with Aroclor 1 2 5 4 (AC) have been widely used to extend the ability of the Salmonella mutagenicity assay t o detect such nondirect-acting agents. We compared the mutagen-activating capabilities of liver S-9 preparations f r o m both Syrian golden hamsters and Sprague-Dawley rats. T h e comparison was made between S-9 fractions from untreated, and phenobarbital (PB)-and AC-treated animals of both sexes. Also compared was the effect of varying the amount of S-9 protein. T h e preparations from hamster liver were consistently more effective than preparations from rat liver for the activation of 2-acetylaminofluorene (AAF), 2-aminoanthracene (AA) (except for ACinduced preparations), 3-methylcholanthrene (MCA), and diethylnitrosamine (DEN) t o their mutagenic forms. Induced preparations from rats were more active than those from hamsters when using benzo(a)pyrene (BP), while with uninduced preparations, the opposite was true.There was also a relationship between the a m o u n t of S-9 protein and the number of revertant colonies obtained. With the aromatic aniines ( A A F and AA), a partial inhibition of mutagenicity occurred at the highest protein concentrations tested. With BP, a n inverse relationship was observed between protein concentration and the number of revertants occurring in the presence of the preparation from PB-and AC-induced male and female rats.T h e relative order of activities of aryl hydrocarbon hydroxylase (AHH) and BP-4,Sepoxide hydrase (EH) in the preparations was AC-induced > PBllie abbreviations used are: AC.

Estimation of the dermal carcinogenic activity of petroleum fractions using a modified Ames assay

“…These results are consistent with the data of Raineri et al (1981) that hamster liver S-9 provides more effective metabolism of 3-methylcholanthrene, and with our experimental evidence that the increased metabolic capacity of the activation mixture is crucial to enhanced mutagenesis.…”

Five of 12 forms of vaccinia virus-expressed human hepatic cytochrome P450 metabolically activate aflatoxin B1.

“…Mutagenesis assays were performed as described (24,25), with each assay mixture containing 3 mg of total lysate protein from vacciniainfected cells. To analyze aflatoxin B1 binding to DNA, =6 x 106 cells were infected with recombinant vaccinia virus and [3H]aflatoxin B1 (15 Ci/mmol, Moravek Biochemicals, San Francisco, CA; 1 Ci = 37 GBq) was added to 13 ml of culture medium in a 10-cm-diameter dish.…”

Predicting carcinogenicity of petroleum distillation fractions using a modified Salmonella mutagenicity assay

“…The superiority of hamster S-9 for the activation of complex PAH mixtures was suggested by several studies (Raineri et al, 1981;Amacher and Turner, 1980;Oberly et al, 1982). Raineri et al (1981) showed that induced hamster S-9 is superior for activation of 3-methyl-cholanthrene, but somewhat less effective than the rat preparation for B[a]P, while Oberly et al (1982) showed approximately equal mutagenicity of 3-methylcholanthrene and dimethylbenzanthracene in the mouse lymphoma assay using rat, mouse, or hamster S-9. However, in the latter study, considerably less toxicity was induced at a given concentration with the hamster preparation.…”

“…Instead of the standard Aroclor 1254-induced rat liver S-9, a corresponding preparation from Syrian golden hamsters is used, and the level of the required cofactor, NADP, has been increased from 4 to 8 mM. The superiority of hamster S-9 for the activation of complex PAH mixtures was suggested by several studies (Raineri et al, 1981;Amacher and Turner, 1980;Oberly et al, 1982). Raineri et al (1981) showed that induced hamster S-9 is superior for activation of 3-methyl-cholanthrene, but somewhat less effective than the rat preparation for B[a]P, while Oberly et al (1982) showed approximately equal mutagenicity of 3-methylcholanthrene and dimethylbenzanthracene in the mouse lymphoma assay using rat, mouse, or hamster S-9.…”