ROLE OF NITRIC-OXIDE IN RENAL HEMODYNAMIC ABNORMALITIES OF CYCLOSPORINE NEPHROTOXICITY

To evaluate the participation of nitric oxide (NO) in chronic cyclospo rin A (CsA) nephrotoxicity, the glomerular hemodynamic response to NO inhibition with N-nitro-L-arginine-methyl-ester (NAME) and stimulation of NO production with L-arginine was studied in uninephrectomized rat s. Chronic CsA administration produced renal vasoconstriction, charact erized by increased afferent (A(R)) and efferent (E(R)) resistances, d ecrease of glomerular plasma flow (Q(A)) and ultrafiltration coefficie nt (K-f) that resulted in a 53% fall of single-nephron glomerular filt ration rate (SNGFR). NAME infusion in vehicle group (V) elevated mean arterial pressure (MAP), A(R) and E(R), reduced Q(A) and K-f, and incr eased glomerular capillary pressure (P-GC), resulting in a 28.9% fall of SNGFR. In the CsA group, NAME also increased MAP, but renal vasocon striction was more intense; a greater rise of AR lowered P-GC (P < 0.0 5 vs. V) further decreasing SNGFR by 38.9%. In control rats, L-arginin e infusion induced a vasodilatory response of A(R) and E(R), and eleva tion of Q(A) and K-f, which resulted in a 72.6% increase in SNGFR. In the CsA group, greater vasodilation was observed and SNGFR rose by 114 .9%. NO2-/NO3- urinary excretion was similar in CsA and V groups, and it was not modified by NAME in either group, but it increased five- to sixfold during L-arginine infusion in both groups. In conclusion, in CsA nephrotoxicity NO production seems to be normal and the ability of the renal endothelium to produce NO is maintained. Therefore renal va so-constriction associated with CsA is not mediated by NO deficiency, although NO appears to attenuate it.