Evidence for peroxynitrite formation in renal ischemia-reperfusion injury:Studies with the inducible nitric oxide synthase inhibitor L-N-6-(1-iminoethyl)lysine

Reactive oxygen species are suggested to participate in ischemia-reperfusio n (I-R) injury. However, induction of inducible nitric oxide synthase (iNOS ) and production of high levels of nitric oxide (NO) also contribute to thi s injury. NO can combine with superoxide to form the potent oxidant peroxyn itrite (ONOO-). NO and ONOO- were investigated in a rat model of renal I-R injury using the selective iNOS inhibitor L-N-6-(1-iminoethyl) lysine (L-NI L). Sprague-Dawley rats were subjected to 40 min of bilateral renal ischemi a followed by 6 h of reperfusion with or without L-NIL administration. Cont rol animals received a sham surgery and had plasma creatinine values of 0.4 +/- 0.1 mg/dl. I-R surgery significantly increased plasma creatinine level s to 1.9 +/- 0.3 mg/dl (P < .05) and caused renal cortical necrosis. L-NIL administration (3 mg/kg) in animals subjected to I-R significantly decrease d plasma creatinine levels to 1.2 +/- 0.10 mg/dl (P < .05 compared with I-R ) and reduced tubular damage. ONOO- formation was evaluated by detecting 3- nitrotyrosine-protein adducts, a stable biomarker of ONOO- formation. Immun ohistochemistry and HPLC revealed that the kidneys from I-R animals had inc reased levels of 3-nitrotyrosine-protein adducts compared with control anim als. L-NIL-treated rats (3 mg/kg) subjected to I-R showed decreased levels of 3-nitrotyrosine-protein adducts. These results support the hypothesis th at iNOS-generated NO mediates damage in I-R injury possibly through ONOO- f ormation.