The role of nitric oxide in iron-induced rat renal injury.
Iron overload and enhanced hydroxyl radical (*OH) formation have been implicated as the causative factors of oxidative stress in different organs. Both pro-oxidant and anti-oxidant properties have been reported for nitric oxide (NO) in iron-mediated tissue injury. To determine the contribution of NO to iron-induced renal injury, eight groups of rats (eight in each group) were studied as follows: control (normal saline), L-Arg (L-arginine as a substrate of NO synthase, 400 mg/kg), L-NAME (an inhibitor of NO synthase, 8 mg/kg), Fe (iron dextran, 600 mg/kg), DFO (deferroxamine as a chelator of iron, 150 mg/kg), Fe+L-Arg, Fe+L-NAME, DFO+L-Arg. Twenty-four hours after the injections, blood samples were taken and kidneys removed for biochemical analysis. Plasma creatinine and urea were used to stimulate renal function. Renal tissue and plasma vitamin E levels, the most important endogenous fat soluble antioxidant, were measured by HPLC and UV detection. In this study, renal function was markedly reduced in the Fe group compared to controls (creatinine, 1.02+/-0.05 mg/dL versus 0.78+/-0.04 P <0.05; urea, 49.59+/-1.69 mg/dL versus 40.75+/-0.86, P <0.01). Vitamin E levels were significantly lower in the Fe group compared to controls (plasma P <0.01; renal tissue P <0.05). Administration of L-Arg to Fe-treated groups prevented these reductions. L-NAME increased iron-induced toxicity significantly, demonstrated by further reduction in the vitamin E levels and renal function compared to the Fe group alone. We concluded that NO plays an important role in protecting the kidney from iron-induced nephrotoxicity. NO synthase blockade enhances iron-mediated renal toxicity in this model.