ABSTRACT
An Aroclor-induced rat hepatic S-9 metabolic activation system was incorporated into the BALB/3T3 cell transformation assay to increase its sensitivity to a wide range of procarcinogens. S-9 was prepared from Aroclor 1254-induced (500 mg/kg) Fischer 344 rats. Cyclophosphamide, dimethylnitrosamine, 2-aminofluorene, and 2-naphthylamine were metabolized to reactive forms capable of inducing both dose-dependent toxicity and morphological transformation of BALB/3T3 cells. Treatments without an exogenous metabolic activation system were nontoxic and nontransforming. Adaptation of this commonly used exogenous metabolic activation system to BALB/3T3 cells will allow detection of the transforming potential of procarcinogens which test negative in a standard assay.
Subject(s)
Carcinogens/toxicity , Cell Transformation, Neoplastic , 2-Naphthylamine/pharmacokinetics , 2-Naphthylamine/toxicity , Animals , Biotransformation , Carcinogenicity Tests , Carcinogens/pharmacokinetics , Cell Line , Cyclophosphamide/pharmacokinetics , Cyclophosphamide/toxicity , Dimethylnitrosamine/pharmacokinetics , Dimethylnitrosamine/toxicity , Dose-Response Relationship, Drug , Fluorenes/pharmacokinetics , Fluorenes/toxicity , Male , Mice , Mice, Inbred BALB C , Microsomes, Liver/metabolism , Rats , Rats, Inbred F344ABSTRACT
When cells were exposed simultaneously for a 24-h period to the poly(ADP-ribose) synthetase inhibitor 3-aminobenzamide (3AB) (1 or 3 mM) plus aflatoxin B1 (AfB1), no increase in toxicity and limited enhancement of transformation frequency (less than 2 X) was observed. Similarly, simultaneous treatment of cell with 3AB plus methylcholanthrene (MCA) had limited effects, slightly decreasing both toxicity and transformation. In contrast, simultaneous treatment with non-toxic doses of 3AB together with the alkylating agents N-methyl-N'-N-nitro-nitrosoguanidine (MNNG) or ethyl methanesulfonate (EMS) resulted in substantial enhancement of the toxicity and transforming effects of both short-chain alkylating agents. When EMS and varying doses of 3AB (0.1-3 mM) were administered simultaneously for 24 h, increasing levels of 3AB were found to cause a dose-dependent enhancement in toxicity and transformation. To explore the relationship of MNNG- and 3AB-induced effects, two further experiments were performed. First, cells were treated with MNNG plus 3AB for varying lengths of time (4, 24, 72 h). Although exposure for as little as 4 h enhanced toxicity and transformation, these effects were even more profound following 24 or 72 h exposure. Second, cells were exposed to 3AB for varing times prior to or after MNNG exposure. Under these conditions the addition of 3AB up to 6 h post MNNG exposure caused profound enhancement of toxicity and transformation, whereas addition of 3AB 24 h post exposure had minimal effects. Thus the co-carcinogenic effect of 3AB is agent-specific, time-specific and dose-dependent.
Subject(s)
Benzamides/pharmacology , Carcinogens/toxicity , Cell Transformation, Neoplastic/drug effects , Aflatoxin B1 , Aflatoxins/toxicity , Animals , Cells, Cultured , Clone Cells , Ethyl Methanesulfonate/toxicity , Kinetics , Methylcholanthrene/toxicity , Methylnitronitrosoguanidine/toxicity , Mice , Mice, Inbred BALB CABSTRACT
3-Aminobenzamide, a potent inhibitor of nuclear poly ADP-ribosyl synthetase, was tested for its ability to alter the toxic and/or transforming effects of ethyl methanesulfonate, methyl methanesulfonate and 3-methylcholanthrene in BALB/3T3 clone A31-1 cells. 3-Aminobenzamide enhanced the toxic effects of both ethyl methanesulfonate and methyl methanesulfonate in a dose dependent manner, but had minimal effects on 3-methylcholanthrene induced toxicity. Similarly, 3-aminobenzamide greatly enhanced ethyl methanesulfonate induced transformation while failing to enhance the transformation of BALB/3T3 clone A31-1 cells by 3-methylcholanthrene. These results stress the importance of poly ADP-ribosyl synthetase in repair of DNA damage and the chemical induction of transformation in vitro.
