Immunochemical Evidence against the Involvement of Cysteine Conjugate [small beta, Greek]-lyase in Compound A Nephrotoxicity in Rats

Background: Compound A, a degradation product of sevoflurane, causes renal corticomedullary necrosis in rats. Although the toxicity of this compound was originally hypothesized to result from the biotransformation of its cysteine conjugates into toxic thionoacyl halide metabolites by renal cysteine conjugate small beta, Greek]-lyase, recent evidence suggests that alternative mechanisms may be responsible for compound A nephrotoxicity. The aim of this study was to evaluate these issues by determining whether mercapturates and glutathione conjugates of compound A could produce renal corticomedullary necrosis in rats, similar to compound A, and whether renal covalent adducts of the thionacyl halide metabolite of compound A could be detected immunochemically.

Methods: Male Wistar rats were administered, intraperitoneally, N-acetylcysteine conjugates (mercapturates) of compound A (90 or 180 micro sign]mol/kg) or glutathione conjugates of compound A (180 micro sign]mol/kg) with or without intraperitoneal pretreatments with aminooxyacetic acid (500 micro sign]mol/kg) or acivicin (250 micro sign]mol/kg). Rats were killed after 24 h, and kidney tissues were analyzed for toxicity by histologic examination or for protein adducts by immunoblotting or immunohistochemical analysis, using antisera raised against the covalently bound thionoacyl halide metabolite of compound A.

Results: Mercapturates and glutathione conjugates of compound A both produced renal corticomedullary necrosis similar to that caused by compound A. Aminooxyacetic acid, an inhibitor of renal cysteine conjugate small beta, Greek]-lyase, did not inhibit the toxicity of the mercapturates, whereas acivicin, an inhibitor of small gamma, Greek]-glutamyltranspeptidase, potentiated the toxicity of both classes of conjugates. No immunochemical evidence for renal protein adducts of the thionacyl halide metabolite was found in rats 24 h after the administration of the mercapturates of compound A or in the kidneys of rats, obtained from a previous study, 5 and 24 h after the administration of compound A.