1.Isolated proximal tubular cells from rat kidney as an in vitro model for studies on nephrotoxicity. II. Alpha-methylglucose uptake as a sensitive parameter for mechanistic studies of acute toxicity by xenobiotics.
Boogaard PJ1, Mulder GJ, Nagelkerke JF. Toxicol Appl Pharmacol. 1989 Oct;101(1):144-57.
Many nephrotoxic agents exert their effect primarily on the cells of the proximal tubules. We isolated these cells and investigated whether the uptake of alpha-methylglucose (alpha-MG) could serve as a parameter to assess effects of nephrotoxins on the functional integrity of the cells. Agents that are acutely nephrotoxic in vivo, CD2+, Hg2+, UO22+, p-aminophenol, and bis-2,3-dibromopropylphosphate, inhibited alpha-MG uptake at low concentrations. Most agents that exert their effect in vivo with delay or only when used chronically (gentamicin, cephaloridine, phenacetin, and acetaminophen) inhibited alpha-MG uptake only at much higher concentrations; cisplatin, however, inhibited alpha-MG uptake at a low concentration. S-(1,1-Difluoro-2,2-dichloroethyl)-L-cysteine and its N-acetyl derivate, two metabolites of the nephrotoxic agent 1,1-dichloro-2,2-difluoroethylene, inhibit alpha-MG uptake. Aminooxyacetic acid, which prevents the formation of the ultimate toxic metabolite by inhibition of beta-lyase, abolished almost completely the toxicity of both compounds.
2.Nephrotoxicity of mercapturic acids of three structurally related 2,2-difluoroethylenes in the rat. Indications for different bioactivation mechanisms.
Commandeur JN1, Brakenhoff JP, De Kanter FJ, Vermeulen NP. Biochem Pharmacol. 1988 Dec 1;37(23):4495-504.
The biotransformation and the hepato- and nephrotoxicity of the mercapturic acids (N-acetyl-1-cysteine S-conjugates) of three structurally related 2,2-difluoroethylenes were investigated in vivo in the rat. All mercapturic acids appeared to cause nephrotoxicity, without any measureable effect on the liver. The mercapturic acid of tetrafluoroethylene (TFE-NAC) appeared to be the most potent nephrotoxin, causing toxicity upon an i.p. dose of 50 mumol/kg. The mercapturic acids of 1,1-dichloro-2,2-difluoroethylene (DCDFE-NAC) and 1,1-dibromo-2,2-difluoroethylene (DBDFE-NAC) were nephrotoxic at slightly higher doses, i.e. at 75 and 100 mumol/kg, respectively. In the urine of TFE-NAC-treated rats significant amounts of difluoroacetic acid (DFAA) could be detected. With increasing doses, the relative amount of DFAA in urine increased progressively (5-18% of dose). In urine of rats treated with DCDFE-NAC and DBDFE-NAC, however, the corresponding dihaloacetic acids, dichloroacetic acid and dibromoacetic acid, could not be detected.
3.Nephrotoxicity and hepatotoxicity of 1,1-dichloro-2,2-difluoroethylene in the rat. Indications for differential mechanisms of bioactivation.
Commandeur JN1, Oostendorp RA, Schoofs PR, Xu B, Vermeulen NP. Biochem Pharmacol. 1987 Dec 15;36(24):4229-37.
1,1-Dichloro-2,2-difluoroethylene (DCDFE) produced marked nephrotoxicity in rats upon an i.p. dose of 150 mumole/kg. At doses higher than 375 mumole/kg, DCDFE also produced hepatotoxicity. Aminooxyacetic acid, an inhibitor of cysteine conjugate beta-lyase, appeared to be slightly nephrotoxic in Wistar rats. Nevertheless it exerted an inhibitory effect on the nephrotoxicity of DCDFE. The N-acetylcysteine conjugate of DCDFE was identified as a major urinary metabolite of DCDFE. When administered as such, this conjugate appeared to be a potent nephrotoxin, without any effect on the liver, indicating that glutathione conjugation of DCDFE is most likely a bioactivation step for nephrotoxicity. The appearance of traces of chlorodifluoroacetic acid in urine of rats treated with higher doses of DCDFE indicates the existence of an oxidative pathway of metabolism of DCDFE, probably involving epoxidation by hepatic mixed-function oxidases. It is speculated that the latter route might account for the hepatotoxicity at higher doses of DCDFE.
4.Effect of beta-naphthoflavone and phenobarbital on the nephrotoxicity of chlorotrifluoroethylene and 1,1-dichloro-2,2-difluoroethylene in the rat.
Morel G1, Ban M, Bonnet P, Zissu D, Brondeau MT. J Appl Toxicol. 2005 Mar-Apr;25(2):153-65.
The role of cytochrome P450 activity in the nephrotoxicity of chlorotrifluoroethylene (CTFE) and 1,1-dichloro-2,2-difluoroethylene (DCDFE) was investigated in the male rat. Hepatic cytochrome P450 1A1 and principally P450 2B1/2 were induced by beta-naphthoflavone and phenobarbital, respectively. Nephrotoxicity was evaluated by investigating urine biochemical parameters, kidney histochemistry and histopathological modifications. Both CTFE and DCDFE induce severe nephrotoxicity in rats after 4 h of exposure to 200 and 100 ppm, respectively. Compared with controls, activity levels of gamma-glutamyltranspeptidase (gamma GT), aspartate aminotransferase (AST), alkaline phosphatase (ALP) and N-acetyl-beta-D-glucosaminidase (NAG) in 24-h urine were increased similarly, but urinary excretion of glucose, proteins and beta2-microglobulin (beta2-m) and serum urea and creatinine levels were increased. Histopathological and histochemical examinations of kidney sections of CTFE- and DCDFE-exposed rats revealed cellular necrosis and tubular lesions 24 h after exposure.