Inhibition of inducible nitric oxide synthase reduces lipopolysaccharide‐induced renal injury in the rat

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Abstract
1. Gram-negative bacterial lipopolysaccharide (LPS) release and subsequent septic shock is a major cause of death in intensive care units. Lipopolysaccharide has been reported to increase the production of nitric oxide (NO) and the formation of oxygen-derived free radicals (OFR) in different organs. The aim of the present study was to evaluate the role of an inducible form of NO synthase (iNOS) and OFR production in LPS-induced renal impairment. 2. Measurement of vitamin E as the most important fat-soluble anti-oxidant was used as a marker of tissue oxidative stress. Lipopolysaccharide (10 mg/kg), L-iminoethyl lysine (L-Nil; 3 mg/kg, i.p.; a specific inhibitor of iNOS activity) and dimethyl thiourea (DMTU; 500 mg/kg i.p.; a well-known OFR scavenger) were used. Four groups of eight rats were studied. One group received LPS, whereas a second group received LPS + L-Nil. A third group received LPS + DMTU and the fourth group, receiving saline, acted as a control group. To evaluate renal function, plasma creatinine and blood urea nitrogen (BUN) were measured. High-pressure liquid chromatography and ultraviolet detection were used to measure plasma and tissue vitamin E levels. Light microscopy was used to examine histopathological changes in the four groups. 3. Lipopolysaccharide markedly decreased the vitamin E content of renal plasma and tissue (P < 0.05). Administration of L-Nil attenuated renal dysfunction and preserved vitamin E levels. However, DMTU failed to prevent renal injury, as indicated by plasma BUN levels and renal histology, despite the fact that it maintained renal vitamin E levels and increased plasma vitamin E levels. Thus, the overproduction of NO by iNOS may have a role in this model of LPS-induced renal impairment.