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Biotransformation and renal processing of nephrotoxic agents
1Department of Toxicology, University of Würzburg, FRG.
Archives of Toxicology. Supplement. = Archiv Fur Toxikologie. Supplement
|January 1, 1996
Summary
Understanding chemical biotransformation is crucial for predicting nephrotoxicity. This study reveals that kidney toxicity arises from metabolite accumulation or direct bioactivation within the kidney, highlighting the need for toxicokinetic and metabolite analysis in safety testing.
Area of Science:
- Toxicology
- Pharmacology
- Biochemistry
Background:
- Nephrotoxicity is a common endpoint in toxicity studies.
- Mechanisms of chemical biotransformation are increasingly understood as key to renal toxicity.
- Chemicals can cause nephrotoxicity through metabolite accumulation and bioactivation in the kidney or direct intrarenal bioactivation.
Purpose of the Study:
- To elucidate the mechanisms of chemical-induced nephrotoxicity.
- To discuss the roles of biotransformation and toxicokinetics in determining organ and cell selectivity.
- To highlight the importance of including metabolites in toxicity testing.
Main Methods:
- Case studies of hexachlorobutadiene (HCBD) and vinylidene chloride (VDC) were used to illustrate mechanisms.
- Investigation of metabolic pathways, including glutathione conjugation and mercapturic acid formation for HCBD.
- Analysis of the role of specific enzymes like cysteine conjugate beta-lyase and cytochrome P450 in bioactivation.
- Examination of toxicokinetic factors such as renal accumulation via organic anion transporters and first-pass hepatic metabolism.
Main Results:
- HCBD nephrotoxicity involves bioactivation of a glutathione conjugate by renal cysteine conjugate beta-lyase, with transport and enzyme distribution determining selectivity.
- VDC induces nephrotoxicity in male mice via an androgen-dependent cytochrome P450 in proximal tubules, with inhalation route being critical due to high kidney concentrations.
- Hepatic first-pass metabolism significantly reduces VDC's nephrotoxic potential after oral or intraperitoneal administration.
Conclusions:
- Nephrotoxicity mechanisms are diverse, involving either kidney accumulation of metabolites followed by bioactivation or direct bioactivation of the parent compound within the kidney.
- Toxicokinetics and biotransformation pathways, including the role of specific transporters and enzymes, are critical determinants of chemical-induced nephrotoxicity.
- Comprehensive in vitro nephrotoxicity screening requires prior elucidation of toxicokinetics and biotransformation pathways, with metabolites integrated into the testing regimen.