Glutathione Cycle Dependency of Ferric Nitrilotriacetate-Induced Lipid Peroxidation in Mouse Proximal Renal Tubules

Parenteral administration of ferric nitrilotriacetate (Fe-NTA), a known carcinogen in mouse and rat kidneys, enhances iron-dependent lipid peroxidation (LP) and causes acute renal tubular necrosis. We assume that filtered Fe-NTA in vivo is rapidly reduced by cysteine, a component of glutathione which is hydrolyzed by γ-GTP and dipeptidase, and that this reduced iron initiates lipid peroxidation in the lumen. In addition, the fatty acid composition of phospholipids between the cortex and the medulla may differ, because only the proximal tubules (which are located mainly in the cortex) are known to be vulnerable to LP. We tested these assumptions in the present study. Gas chromatographic determination of fatty acid composition in five male and five female 6-week-old normal ddY mice showed the ratio of polyunsaturated fatty acids to saturated fatty acids plus C18:1, a single double-bond fatty acid, to be 0.98 ± 0.08 (av ± SD) in the male cortex and 1.00 ± 0.08 in the female cortex. In the male and female medulla, however, it was 0.78 ± 0.09 (P > 0.05, vs cortex) and 0.68 ± 0.04 (P > 0.01, vs cortex), respectively. Pretreatment of the animals with buthionine sulfoximine, a glutathione synthetase inhibitor, and a procedure that reduces total glutathione content in the kidneys, suppressed LP. Reduced thiobarbituric acid reactive substances were also observed in animals treated with AT-125, a γ-GTP inhibitor, and in animals with immature γ-GTP activity. These results are consistent with our assumptions.