@article {Bjercke759, author = {R J Bjercke and D K Hammond and H W Strobel and J J Langone}, title = {Interaction of cotinine with rat hepatic microsomal P-450. Comparison with metyrapone and immunomodulation of cotinine and metyrapone binding by monoclonal anti-cotinine antibodies.}, volume = {18}, number = {5}, pages = {759--764}, year = {1990}, publisher = {American Society for Pharmacology and Experimental Therapeutics}, abstract = {The ability of the major nicotine metabolite, cotinine, to interact with rat liver microsomal cytochrome P-450 and the immunomodulatory effects of anti-cotinine antibodies were studied. Cotinine induced type II spectral changes with both microsomes from phenobarbital (PB)-induced rats and purified P-450 with apparent Ks values of 97 and 750 microM, respectively. In contrast, the Ks value was 0.3 microM for metyrapone and 5 microM for nicotine with both the microsomes and purified enzyme. The apparent Ki value for cotinine inhibition of 7-pentoxyresorufin O-dealkylase activity with the microsomes (87 microM) was approximately 87- and 870-fold higher than for nicotine and metyrapone, respectively. Monoclonal antibodies produced against cotinine cross-reacted equally well with metyrapone. They specifically blocked enzyme binding of both drugs based on dose-dependent inhibition of spectral changes, and reversed the metyrapone-induced inhibition of microsomal O-dealkylase activity. In contrast, antibodies to nicotine did not cross-react with cotinine or metyrapone and had no effect on their activity, although they did block the action of nicotine. These results demonstrate that cotinine binding to P-450 from PB-induced rats and inhibition of functional activity in vitro are qualitatively like the effects of metyrapone and nicotine, and that monoclonal anti-cotinine antibodies are useful molecular probes of the interactions between cotinine and metyrapone with the enzyme.}, issn = {0090-9556}, URL = {https://dmd.aspetjournals.org/content/18/5/759}, eprint = {https://dmd.aspetjournals.org/content/18/5/759.full.pdf}, journal = {Drug Metabolism and Disposition} }