Toxic nephropathy: environmental chemicals

The kidney is the target of numerous xenobiotic toxicants, including environmental chemicals. Anatomical, physiological, and biochemical features of the kidney make it particularly sensitive to many environmental compounds. Factors contributing to the sensitivity of the kidney include: large blood flow, the presence of a variety of xenobiotic transporters and metabolizing enzymes, and concentration of solutes during urine production. In many cases, the conjugation of environmental chemicals to glutathione and/or cysteine targets these chemicals to the kidney where inhibition of renal function occurs through a variety of mechanisms. For example, heavy metals such as mercury and cadmium target the kidney after glutathione/cysteine conjugation. Trichloroethlene and bromobenzene are metabolized and conjugated to glutathione in the liver before renal uptake and toxicity. In contrast, renal injury produced by chloroform and aristolochic acids is dependent on renal cytochrome P450 metabolism to toxic metabolites. Other compounds, such as paraquat or diquat, damage the kidney via the production of reactive oxygen species. Finally, the low solubility of ethylene glycol metabolites causes crystal formation within the tubular lumen and nephrotoxicity. This chapter explores mechanisms of nephrotoxicity by environmental chemicals, using these example compounds. What remains to be accomplished and by far the most difficult process is the elucidation of the detailed mechanisms of tubular cell injury after toxicant uptake and metabolism. The large number of individuals experiencing a decline in renal function with age makes the search for these mechanisms very compelling.