Tissue and species differences in enzymes of epoxide metabolism

1. Glutathione transferase and epoxide hydratase activities were determined in liver, lung and kidney of nine species including man with [7-3H]styrene oxide as substrate. 2. Activity was detectable in all tissues. The activities of both enzymes were higher in the liver of all species than in either kidney or lung. 3. The baboon had the highest hepatic epoxide hydratase activity, 31 +/- 2 nmol/mg per min, while the mouse had the lowest hepatic activity, 1.9 +/- 0.1 nmol/mg per min. 4. Rodent species had higher glutathione transferase activity than non-rodent species, mouse liver having the highest activity, 143 +/- 13 nmol conjugate/mg per min. 5. Taking all the data into account, it is concluded that no single species of those studied is a suitable model for the disposition of epoxides in man.