L-ARGININE AND ALLOPURINOL PROTECT AGAINST CYCLOSPORINE NEPHROTOXICITY

The role of nitric oxide (NO) and oxygen free radicals in cyclosporine (CsA) nephrotoxicity was investigated using L-arginine, an NO substra te, and allopurinol, a xanthine oxidase inhibitor (involved in the for mation of oxygen radicals) in an experimental model with Wistar rats. CsA, administered at 15 mg/kg/body weight (BW) subcutaneously for 10 d ays, caused a decrease in glomerular filtration rate, with inulin clea rance of 0.33+/-0.04 vs. 1.11+/-0.06 ml/min/100 g BW (P<0.01 vs. contr ol). L-Arginine, 1.5% in drinking water 5 days before and during CsA a dministration partially protected the animals against this fall in glo merular filtration rate, with inulin clearance of 0.68+/-0.03 ml/min/1 00 g BW (P<0.01 vs. CsA). Allopurinol, at 10 mg/kg/BW by gavage, also had a protective action, with inulin clearance of 0.54+/-0.04 ml/min/1 00 g (P<0.01 vs. CsA). CsA caused an elevation in NO production, as as sessed by urinary excretion of its metabolites, nitrite and nitrate (N O2 and NO3; 0.836+/-0.358 vs. 0.107+/-0.019 nmol/mu g creatinine). NO production was as much as threefold higher in the L-arginine group (1. 853+/-0.206 nmol/g creatinine). This CsA effect is probably related to its vasoconstrictive stimulus. Supplementation with L-arginine, which provides more substrate for NO formation, may enhance vasodilatation and consequently reduce the impairment of renal function. The protecti on provided by allopurinol may be related to the reduced formation of oxygen radicals, preventing the deleterious effects of lipid peroxidat ion.