Reductive metabolism of heptachlor,parathion, 4,4′-dichlorobenzophenone,and carbophenothion by rat liver systems

An attempt was made to survey systems which carry out reduction of four pesticidal chemicals, heptachlor, parathion, 4,4-dichlorobenzophenone, and carbophenothion sulfoxide, in rat liver microsomes and in the supernatant in vitro. On the basis of the stimulatory effects of nicotinamide cofactors (NADPH and NADH), a flavin cofactor (FAD), localization of the systems, and their sensitivities to heat-inactivation treatment, four different reductive systems were recognized. They are (a) the mixed-function oxidase-coupled reductive systems, (b) an independent NADH-stimulated (instead of NADPH as above) microsomal system for parathion reduction, (c) FAD-stimulated system for reduction of carbophenothion sulfoxide and parathion, present specifically in the supernatant, and (d) a heat stable, nonenzymatic reduction system in the microsomes operated by flavoproteins and a flavin cofactor.