Nephrotoxicity of chloroform: metabolism to phosgene by the mouse kidney.

In this investigation, we have attempted to determine whether chloroform (CHCl3)-induced nephrotoxicity might be due to its metabolism to phosgene (COCl2) in the kidney. We have found that kidney homogenates from DBA/2J male mice in the presence of glutathione metabolize CHCl3 to 2-oxothiazolidine-4-carboxylic acid (OTZ). This product appears to be formed by the initial trapping of COCl2 by two molecules of GSH to form diglutathionyl dithiocarbonate (GSCOSG). Kidney gamma-glutamyl transpeptidase can rapidly metabolize GSCOSG to N-(2-oxothiazolidine-4-carbonyl)-glycine which is then hydrolyzed, possibly by cysteinyl glycinase to OTZ. The finding that deuterium-labeled chloroform (CDCl3) was less nephrotoxic and depleted less renal GSH than did CHCl3 suggests that the metabolism of CHCl3 to COCl2 may also occur in the kidney in vivo and lead to nephrotoxicity.

The formation of diglutathionyl dithiocarbonate as a metabolite of chloroform, bromotrichloromethane, and carbon tetrachloride.

One hour after the intraperitoneal administration of CHCl3, CBrCl3, or CCl4 to phenobarbital (PB)-treated rats, hepatic GSH levels decreased to 30, 59, and 88% of control levels, respectively; after 4 hr, the GSH levels had returned to 46, 65, 99%, respectively, of control levels. When incubated for 15 min in air with rat liver microsomes from PB-treated rats, a NADPH-generating system, and GSH (5 mM), all of the compounds were converted to diglutathionyl dithiocarbonate (GSCOSG). The rate of conversion of CHCl3, CBrCl3, and CCl4 to GSCOSG was 180, 58, and 8 nmol per mg of protein per 15 min, respectively. The GSCOSG was also identified in bile by 13C-NMR spectroscopy and HPLC as an in vivo metabolite of CHCl(3), CBrCl3, and CCl4. After the administration of CHCl3, CBrCl3, and CCl4, 2.89, 0.64, or 0.11 mumol of GSCOSG, respectively, was excreted in 6 hr. These results suggest that CHCl3, CBrCl3, and CCl4 are metabolized in vitro and in vivo to phosgene (COCl2), which reacts with GSH to produce GSCOSG. The reaction of GSH with COCl2 may be responsible at least in part for the GSH-depleting properties of CHCl3, CBrCl3, and CCl4, inasmuch as the relative amounts of formation of GSCOSG in vitro and in vivo paralleled their relative GSH-depleting activities.