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Commercial formulations of the pesticides: Guthion (azinphos methyl), Sencor (metribuzin), Lorox (linuron), Reglone (diquat), Daconil (chlorothalonil) and Admire (imidacloprid) were studied for their genotoxicity by 32P-postlabeling. Metabolites of the pesticides were obtained enzymatically using arochlor induced rat liver S9 fraction, in an NADPH generating system. The resulting metabolites were reacted with calf thymus DNA and the DNA was analyzed for presence of adducts by either the nuclease P1 or butanol enrichment. Nuclease P1 enrichment resulted in adducts for all the pesticides. Compared to the level of adducts in control DNA, the levels in pesticide-treated DNA were higher for all the pesticides, except Daconil. The increase in adduct numbers for pesticide-treated DNAs ranged from 4.9-12.4 times the control-DNA indicating pesticide genotoxicity in this in vitro system. Enrichment using butanol extraction gave three adducts unique to Sencor-DNA. These adducts were different from those obtained with nuclease P1 enrichment of the same. B(α)P was the positive control for the in vitro metabolism, and two adduct enrichment procedures: nuclease P1 digestion and butanol extraction.

A microfluorometric method for the detection of low levels of cytochrome P450 was developed to increase the sensitivity of the assay, since a low level of CYP450 associated enzymatic activities was expected in human placenta tissues and small samples of placenta (∼10 g) could be easily collected, stored and processed. The dual fluorescence assay of Kennedy et al. [1], which was developed to simultaneously quantitate microsomal proteins and ethoxyresorufin-O-deethylase (EROD) activity was adapted for 96 wells microtiter plates. Placental microsomes samples were analyzed. For samples obtained from non-smoking mothers from the general southern Quebec population, results ranged from less than 1–3.3 pmol/mg protein•min. Samples collected from smoking mothers showed activity levels ranging from 30–69 pmol/mg protein•min. These results showed the suitability of the microassay for measuring low level of CYP450 activity in tissues such as placenta. (Mol Cell Biochem 175: 131–136, 1997)