MONOOXYGENASE-CATALYZED ALDRIN EPOXIDATION AND DIHYDROISODRIN HYDROXYLATION IN MONKEY LIVER NEEDLE-BIOPSY SPECIMENS - ASSAY AND PROPERTIES

  • 1 January 1976
    • journal article
    • research article
    • Vol. 4  (1) , 28-34
Abstract
Aldrin epoxiation and dihydroisodrin (1,8,9,10,11,11-hexachloro-2,3-7,6-endo-2,1-7,8-endo-tetracyclo[6.2.1.13,6.02,7]dodec-9-ene (DHI) hydroxylation were 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 02, and both transformations were inhibited by C0. The apparent KM and Vmax [maximal velocity] (.+-. SD) for epoxidation was 1.2 .+-. 0.2 .times. 10-5 M aldrin and 210 .+-. 20 pmol dieldrin/mg protein per min, and the corresponding values for nydroxylation were 2.3 .+-. 0.4 .+-. 10-5M DHI and 150 .+-. 20 pmol DHI-OH/mg 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.