Metabolism of a dicofol impurity alpha-chloro-DDT, but not dicofol or dechlorodicofol, to DDE in mice and a liver microsomal system.

1. The important acaricide dicofol and two related compounds, alpha-chloro-DDT (an impurity in dicofol) and dechlorodicofol (DCD) (a photolysis product of dicofol), as [phenyl-14C]-labelled preparations, were administered i.p. to male mice (30 mg/kg) and incubated with rat-liver microsomes alone and with NADPH, both aerobically and anaerobically, and with rat-liver cytosol alone and with glutathione. 2. alpha-Chloro-DDT is metabolically dechlorinated to DDE in the following systems: in vivo, based on analyses of mouse brain, fat and liver; in vitro, with anaerobic rat-liver microsomes plus NADPH; and with reduced haematin. Trace amounts of DDT are also detected in vivo in mouse liver. 3. Dicofol is reductively dechlorinated to DCD, and both compounds are metabolized to dichlorobenzophenone and dichlorobenzhydrol in vivo in the mouse tissues examined, and also in vitro exclusively with anaerobic rat-liver microsomes in the presence of NADPH. Liver cytosol with glutathione is less effective or inactive. 4. The in vivo metabolic dechlorinations of alpha-chloro-DDT and dicofol probably involve a reduced porphyrin in liver microsomes.