Disulfiram metabolism as a requirement for the inhibition of rat liver mitochondrial low Km aldehyde dehydrogenase

Abstract

In humans and animals, disulfiram produces a disulfiram-ethanol reaction after an ethanol challenge, the basis of which is the inhibition of liver aldehyde dehydrogenase (ALDH). Disulfiram and the metabolites diethyldithiocarbamate (DDTC), diethyldithiocarbamate-methyl ester (DDTC-Me), and S-methyl- N, N-diethylthiolcarbamate (DETC-Me) were studied in order to determine the role of bioactivation in disulfiram's action as an inhibitor of rat liver mitochondrial low K m ALDH (RLM low K m ALDH). In in vitro studies, disulfiram and DDTC (0.01 to 2.0 mM) both inhibited RLM low K m ALDH in a concentration-dependent manner. The addition of rat liver microsomes to the mitochondrial incubation did not further increase disulfiram-induced RLM low K m ALDH inhibition. However, DDTC-induced RLM low K m ALDH inhibition was increased further, but only at DDTC concentrations < 0.05 mM. DDTC-Me and DETC-Me (2.0 mM) similarily exhibited an increased RLM low K m ALDH inhibition after the addition of liver microsomes. In in vivo studies, disulfiram (75 mg/kg), DDTC (114 mg kg ), DDTC-Me (41.2 mg/kg) or DETC-Me (18.6 mg/kg) administered i.p. to female rats inhibited RLM low K m ALDH. Inhibition of drug metabolism by pretreatment of rats with the cytochrome P450 inhibitor N-octylimidazole (NOI) (20 mg/kg, i.p.) prior to either disulfiram, DDTC, DDTC-Me or DETC-Me administration blocked the inhibition of RLM low K m ALDH. The in vitro and in vivo data support the conclusion that bioactivation of disulfiram to a reactive chemical species is required for RLM low K m ALDH inhibition and a disulfiram-ethanol reaction.