Oxidation of diethyldithiocarbamate to disulfiram by liver microsomes in the presence of NADPH and subsequent loss of microsomal enzyme activity in vitro.

Oxidation of diethyldithiocarbamate (DTC) to disulfiram (DS) by liver microsomes was tested in vitro by using a copper-DTC chelate formation reaction after the conversion of DS to DTC by glutathione (GSH). In the presence of NADPH, microsomes produced DS from DTC in both the free and microsome-bound forms, the former being greater than the latter. DS production was dependent on NADPH and DTC concentrations, and incubation time. Increases in microsomal concentrations, up to a certain level, also increased the free and total DS production. NADH was only somewhat effective, both the exposure to a nitrogen atmosphere and heat-denaturation of the microsomes suppressed the reaction. Preincubation of microsomes with both DTC and NADPH markedly decreased aniline hydroxylase, p-nitroanisole O-demethylase and glucose-6-phosphatase activities, and moderately decreased NADH-ferricyanide and NADH-cytochrome c reductase, but NADPH-cytochrome c reductase was minimally affected. DTC alone had only slight effects on the activities. DS also decreased these enzyme activities, particularly glucose-6-phosphatase; the loss of NADPH-cytochrome c reductase activity being protected in the presence of NADPH. GSH almost completely prevented the loss of microsomal enzyme activities induced by DTC and NADPH except for the drug metabolizing activities, in which protection was incomplete. The microsomal oxidation of DTC to DS could play a role in the action of DS in the liver, since DS is rapidly degradated to DTC in vivo.