The cellular effects of the antioxidants butylated hydroxyanisole and butylated hydroxytoluene were studied in a battery of in vitro tests. No evidence of genotoxicity was obtained for either compound in the hepatocyte primary culture/DNA repair test, the Salmonella/microsome mutagenesis test, the adult rat liver epithelial cell/hypoxanthine-guanine phosphoribosyl transferase test, or for butylated hydroxyanisole in the Chinese hamster ovary cell/sister chromatid exchange test. Both compounds inhibited intercellular molecular exchange between cultured liver cells, an effect that has been observed for many agents with neoplasm-promoting activity.

Because mutagens typified by 2-amino-3-methylimidazo[4,5-f]quinoline (IQ) observed in cooked foods are widely consumed, detailed studies of their biochemical and biological properties including carcinogenicity are most important. IQ induces unscheduled DNA synthesis in liver cells, which when taken together with its powerful mutagenicity in the Salmonella typhimurium test system, predicts carcinogenicity. In female Sprague-Dawley rats, IQ did exhibit potent carcinogenicity for the mammary gland, the ear duct, and to a lesser extent, pancreas and bladder. Data from Japanese laboratories indicate carcinogenicity also to the intestinal tract. Thus, one of the mutagens formed during cooking is a versatile carcinogen that because of extensive human intake requires urgent exploration for specific human cancer risk.

The food mutagen 2-amino-3-methylimidazo[4,5-f]quinoline (IQ) is an analogue of quinoline, a hepatocarcinogen. 2-Aminofluorene, benzidine and 3,2'-dimethyl-4-aminobiphenyl (DMAB) are potent inducers of unscheduled DNA repair in primary culture rat liver hepatocytes, as was IQ (151 grains/nucleus at 1 X 10(-6) M). Quinoline, on the other hand, is only weakly positive in this assay (15 grains/nucleus at 1 X 10(-3) M). IQ, quinoline and DMAB were applied topically to shaved skin of Sencar mice with promotion by 12-O-tetradecanoylphorbol 13-acetate (TPA) for 20 weeks, when 14 of 20 mice in the quinoline group had 25 tumors, but only one of 30 animals in the IQ group and five of 30 in the DMAB group were tumor-bearing. Analogs of IQ synthesized by substitution at the 2- or 3-position with amino or methyl groups were assayed with the Ames Salmonella typhimurium tester strains TA98 and TA100. Mutagenicity for TA98 is reduced in the absence of the 3-methyl group and is completely abolished with removal of the 2-amino moiety. None of these analogs are strong mutagens for TA100. Exocyclic N-oxidation is a likely obligatory step in the activation of IQ to a mutagen.

Morpholine and a series of morpholine derivatives were assayed for the potential to induce DNA repair in the rat hepatocyte primary culture/DNA repair assay. Morpholine did not induce DNA repair at dose concentrations which were not toxic (0.0001-0.1 mg/ml). Two animal metabolites of morpholine, N- methylmorpholine oxide and N- hydroxymorpholine , also did not induce DNA repair at the non-toxic concentrations tested (0.0001-10 mg/ml and 0.0001-1 mg/ml, respectively). A putative metabolite of morpholine, 3- morpholinone , was inactive (0.001-10 mg/ml) and a polyurethane foam catalyst, N- butylmorpholine (0.0001-0.1 mg/ml) was also inactive. The chemical intermediate N- hydroxyethylmorpholine induced DNA repair in the dose range 1-5 mg/ml. It was concluded that genotoxicity of substituted morpholines is a function of the substituent moiety rather than morpholine itself.

An assay for mutagenesis at the hypoxanthine-guanine phosphoribosyl transferase (HGPRT) locus in adult rat-liver epithelial cell cultures (ARL) has been developed to take advantage of the capacity of this cell type to metabolically activate promutagens/procarcinogens. A survey of the effect of 5 types of activation-dependent mutagens/carcinogens on 4 ARL lines indicates that the ARL/HGPRT mutagenesis assay with the 4 target cell lines is able to detect a spectrum of activation-dependent carcinogens. Individual ARL lines, however, responded quite differently to a given carcinogen. The ARL/HGPRT mutagenesis assay system thus offers distinct possibilities for the study of the control of chemical biotransformation processes. However, in light of the specificity of the various cell lines to respond to a particular class of mutagens under the current assay condition, this particular assay system cannot be readily applied to routine screening of suspected environmental mutagens of unknown requirements for metabolic activation. Nevertheless, for agents with a structure related to those activated by a specific line, this system can be used to study mutagenesis resulting from intact cellular metabolism.

Polybrominated biphenyls (PBB) were studied for their genotoxic and epigenetic effects in cultured liver cells. PBB did not elicit DNA repair synthesis in rat, mouse, or hamster hepatocytes in primary cultures and did not cause mutations at the hypoxanthine-guanine phosphoribosyl transferase locus in a line of rat liver epithelial cells or in human fibroblasts cocultivated with rat hepatocytes as an activating system. In contrast, PBB inhibited intercellular molecular exchange between rat hepatocytes and liver epithelial cells indicating an epigenetic membrane effect. These data are consistent with the interpretation that PBB act as neoplasm promoters in the production of rodent liver neoplasms.

Annals of the New York Academy of SciencesVolume 407, Issue 1 p. 474-475 COMPARISON OF SISTER CHROMATID EXCHANGE and MAMMALIAN CELL MUTAGENESIS AT THE HYPOXANTHINE GUANINE PHOSPHORIBOSYL TRANSFERASE LOCUS IN ADULT RAT LIVER EPITHELIAL CELLS S. Ved Brat, S. Ved Brat Naylor Dana Institute for Disease Prevention American Health Foundation Valhalla, New York 10595Search for more papers by this authorC. Tong, C. Tong Naylor Dana Institute for Disease Prevention American Health Foundation Valhalla, New York 10595Search for more papers by this authorS. Telang, S. Telang Naylor Dana Institute for Disease Prevention American Health Foundation Valhalla, New York 10595Search for more papers by this authorG. M. Williams, G. M. Williams Naylor Dana Institute for Disease Prevention American Health Foundation Valhalla, New York 10595Search for more papers by this author S. Ved Brat, S. Ved Brat Naylor Dana Institute for Disease Prevention American Health Foundation Valhalla, New York 10595Search for more papers by this authorC. Tong, C. Tong Naylor Dana Institute for Disease Prevention American Health Foundation Valhalla, New York 10595Search for more papers by this authorS. Telang, S. Telang Naylor Dana Institute for Disease Prevention American Health Foundation Valhalla, New York 10595Search for more papers by this authorG. M. Williams, G. M. Williams Naylor Dana Institute for Disease Prevention American Health Foundation Valhalla, New York 10595Search for more papers by this author First published: June 1983 https://doi.org/10.1111/j.1749-6632.1983.tb47868.xCitations: 1AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL No abstract is available for this article.Citing Literature Volume407, Issue1Cellular Systems for Toxicity TestingJune 1983Pages 474-475 RelatedInformation

The organochlorine pesticides chlordane and heptachlor were evaluated for their genotoxicity and epigenetic membrane effects. Both compounds were non-genotoxic in the ARLHGPRT mutagenesis assay in which the genotoxic carcinogens 7, 12-dimethylbenz[a]anthracene and benzo[a]pyrene induced significant increases in mutant incidence. The pesticides both markedly inhibited intercellular communication between cultured liver cells, a property demonstrated by many tumor promoting agents, whereas benzo[a]pyrene did not produce this epigenetic effect.

The amosite, crocidolite, and chrysotile forms of UICC asbestos were assayed for their ability to induce gene mutations at the hypoxanthine-guanine phosphoribosyl transferase locus. Using adult rat liver-derived (ARL-6 and ARL-18) cells in culture, no consistent or significant increase occurred in the number of mutants resistant to the purine analog, 6-thioguanine, after exposure to toxic levels of amosite, crocidolite, or chrysotile. These results support the concept that asbestos is an epigenetic carcinogen that does not alter DNA.

The hepatocyte primary culture (HPC)--DNA repair test and the adult rat liver epithelial cell (ARL)--hypoxanthine-guanine phosphoribosyl transferase (HGPRT) mutagenesis assay are two in vitro short-term tests that possess intrinsic capability for xenobiotic biotransformation. Both assays detected the genotoxicity of a variety of carcinogenic polycyclic aromatic hydrocarbons. Thus, these two tests, which embody intact cellular metabolism, are useful for the evaluation of this class of carcinogens and provide results that strengthen those obtained in tests dependent upon subcellular metabolism.