The role of nitric oxide pathway in the renal ischemia-reperfusion injury in rats.
Nitric oxide (NO), synthesized from L-arginine by the enzyme nitric oxide synthase (NOS), seems to play an ambiguous role during tissue ischemia-reperfusion injury. Our objective was to evaluate the effects of L-arginine, a NO donor, and N(G)-nitro-L-arginine-methylester (L-NAME), a NOS inhibitor, on oxidative stress, renal dysfunction, histologic alterations and surgical mortality rate induced by renal ischemia-reperfusion (RIR) in uninephrectomized rats. One-hundred and ninety-seven Wistar rats were randomized into five experimental groups. Group 1: sham operation; group 2: right uninephrectomy (UNI); group 3: UNI + RIR in the contralateral kidney; group 4: UNI + L-NAME (20 mg/kg; intraperitoneally) + RIR; and group 5: UNI + L-arginine + RIR. The effect of the drugs was evaluated by lipid peroxidation measured by the renal malondialdehyde (MD) content and chemiluminescence (CL) levels, serum creatinine (Cr) levels, urinary volume, tubular necrosis and athrophy, inflammatory infiltrate, interstitial fibrosis as histologic evaluation and surgical mortality rate after the procedures. A P value less than 0.05 was considered significant. Right uninephrectomy did not alter the renal parameters. RIR increased Cr levels (at 24 and 96 h of reperfusion), index of lipid peroxidation (both MD and QL levels), and worsened the histologic aspects. Pretreatment with L-arginine reduced the kidney levels of QL when compared with the non-treated group (5574 +/- 909 vs. 13 660 +/- 1104 cps/mg of protein; P < 0.05) but increased the MD levels (0.97 +/- 0.24 vs. 0.79 +/- 0.06 nmol/mg of protein; P < 0.05). Moreover, L-arginine attenuated the increment of Cr levels, inflammatory infiltrate and tubular athrophy in rats subjected to RIR (P < 0.05). On the other hand, pretreatment with L-NAME increased both CL (17 482 +/- 4397 vs. 13 660 +/- 1104 cps/mg of protein; P < 0.05) and MD levels (1.16 +/- 0.11 vs. 0.79 +/- 0.06 nmol/mg of protein; P < 0.05). Furthermore, L-NAME worsened the renal dysfunction (P < 0.05) at 192 h after the RIR, and surgical mortality rates were similar (P > 0.05). L-arginine has a tendency to exert a beneficial effect on renal damage during RIR in rats. Moreover, L-NAME seems to worsen the renal damage by increasing the kidney-levels of CL and impairment of renal function probably due to reduction of NO production.