[Renal hemodynamic interactions of nitric oxide and angiotensin II]

We have already reported that decreased renal medullary blood flow and retention of sodium play an important role in the development of hypertension during chronic systemic L-NAME (NG-nitro-L-arginine methyl ester) administration, despite the absence of measurable changes in renal cortical blood flow as determined from fibers implanted for laser-Doppler flowmetry. In the present experiment, to investigate the interaction between nitric oxide and angiotensin II on renal hemodynamics, the effect of chronic intravenous infusion of L-NAME on blood pressure, sodium and water retention, and intrarenal blood flow distribution were studied in a separate group of rats pretreated with captopril and in which optical fiber for laser-Doppler flowmetry had been implanted. Captopril completely prevented sustained hypertension, sodium retention, and decreased medullary blood flow during chronic L-NAME infusion. These date indicated that angiotensin plays an important role in the regulation of renal medullary blood flow and sodium excretion by modulating the effects of nitric oxide in renal medullary blood flow.