Monooxygenase-catalyzed aldrin epoxidation and dihydroisodrin hydroxylation in monkey liver needle-biopsy specimens....

Aldrin epoxidation and dihydroisodrin (1,8,9,10,11,11-hexachloro-2,3-7,6-endo-2,1-7,8-endo-tetracyclo [6.2.1.1(3), (6).0(2), (7)]dodec-9-ene (DHI) hydroxylation have been studied in 0.2-ml liver monooxygenase preparations. Liver biopsy specimens of rhesus (Macaca mulatta) and bonnet (M. radiata) monkeys obtained with a 1.9-mm Menghini needle were the primary enzyme sources. Dieldrin and monohydroxydihydroisodrin (DHI-OH) were the only metabolites detected by electron-capture GLC analysis of hexane extracts of incubation media. Incubation, extraction, and analysis could be done in the same vessel. Maximum rates were obtained in the presence of NADPH and O2, and both transformations were inhibited by CO. The apparent KM and Vmax (+/-SD) for epoxidation was 1.2 +/- 0.2 X 10(-5) M aldrin and 210 +/- 20 pmol of dieldrin per mg of protein per min, and the corresponding values for hydroxylation were 2.3 +/- 0.4 X 10(-5) M DHI and 150 +/- 20 pmol of DHI-OH per mg of protein per min. Aldrin epoxidation and DHI hydroxylation activities of rhesus monkey liver biopsy and rat liver preparations were evaluated after phenobarbital treatment. The assay procedures can be used in protocols in which animals serve as their own controls.