Effects of intermittent dichloromethane inhalation on blood carboxyhemoglobin concentration and drug metabolizing enzymes in rat.

Rats were exposed to dichloromethane vapor in concentrations of 500 ppm, 1000 ppm, or 1000 ppm as a time-weighted average. All of the exposures lasted for 6 h, five days a week for two weeks. Kidney microsomes displayed a dose-dependent enhancement of the ethoxy-coumarin O-deethylase activity. After the second week the enhancement was accompanied by an increase in the renal glutathione content. In the liver, the UDP-glucuronosyltransferase activity showed a dose-dependent increase and the NADPH-cytochrome c reductase activity decreased. The hepatic glutathione content remained unchanged. Dichloromethane exposure did not affect the hemoglobin concentration of the blood. An 8 to 9% COHb concentration was found after exposure in all of the study groups. The similarity of COHb concentrations suggest that, in the rat, the metabolic pathway converting dichloromethane to CO is saturated already at the lowest exposure level under study.