Quantitative significance of glutathione and glutathione-S-transferase in regulating benzo[a]pyrene anti diol-epoxide level in reconstituted C3H/10T1/2 cell lysates, and comparison to rat liver.
Induced 10T1/2 cell microsomes were independently reconstituted with [3H]benzo[a]pyrene (BP) and glutathione (GSH) or purified GSH-transferases. Levels of the primary BP anti 7,8-dihydrodiol 9,10-epoxide (r-7,t-8 dihydroxy-t-9,10-oxy-7,8,9,10 tetrahydrobenzo[a]pyrene) hydrolysis product, 7,10/8,9-tetrol, were measured in incubation extracts, enabling us to monitor the level of free anti diol-epoxide in incubations and to determine the independent effects of GSH or GSH-transferases upon it. GSH alone had no effect on anti diol-epoxide levels over the concentration range tested (0-4.0 mM), however, the addition of purified GSH-transferase from rat liver resulted in a dose-dependent conjugation of anti diol-epoxide as well as 9,10-epoxide and 7,8-epoxide with 50% conjugation occurring at 0.036, 0.039 and 0.17 units GSH-transferase/ml, respectively. Free anti diol-epoxide was reduced by greater than 95% when we reconstituted with the GSH-transferase concentration which we measured in 10T1/2 cells (0.15-0.27 units/ml cell cytosol); this GSH-transferase concentration represents only 6% of that found in rat liver. The results suggest that in both 10T1/2 cells and rat hepatocytes GSH-transferase catalyzed GSH conjugation is quantitatively significant in determining the intracellular level of anti diol-epoxide.
D000818:Animals; D001564:Benzo(a)pyrene; D001580:Benzopyrenes / Q000378:metabolism*; D001711:Biotransformation; D002273:Carcinogens / Q000378:metabolism*; D002478:Cells, Cultured; D005978:Glutathione / Q000378:metabolism*; D005982:Glutathione Transferase / Q000378:metabolism*; D007700:Kinetics; D008099:Liver / Q000378:metabolism*; D008297:Male; D051379:Mice; D008809:Mice, Inbred C3H; D008861:Microsomes / Q000378:metabolism; D008862:Microsomes, Liver / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains
D001580:Benzopyrenes; D002273:Carcinogens; D001564:Benzo(a)pyrene; D005982:Glutathione Transferase; D005978:Glutathione