EFFECT OF CHRONIC RENAL MEDULLARY NITRIC-OXIDE INHIBITION ON BLOOD-PRESSURE

The effects of chronic nitric oxide inhibition in the renal medulla on renal cortical and medullary blood flow, sodium balance, and blood pr essure were evaluated in conscious uninephrectomized Sprague-Dawley ra ts. During a Ei-day renal medullary interstitial infusion of the nitri c oxide inhibitor N-G-nitro-L-arginine methyl ester (L-NAME, 120 mu g/ h) in saline (0.5 ml/min), renal medullary blood flow was selectively decreased by 30% after 2 h and was maintained at that level for the en tire infusion. The decrease in medullary blood flow was associated wit h sodium retention and increased blood pressure. After the cessation o f L-NAME infusion, medullary blood flow returned to control, and the s odium balance became negative as blood pressure returned to baseline. These data indicate that renal medullary nitric oxide plays an importa nt role in the regulation of renal blood flow, sodium excretion, and b lood pressure.