Pressure natriuresis following acute and chronic inhibition of nitric oxide synthase in rats. Guarasci, Gregory R., and Robert L. Kline. Department of Physiology, University of Western Ontario, London, Ontario N6A 5C1, Canada
APStracts 2:0234R, 1995.
Pressure natriuresis following acute and chronic inhibition of nitric oxide synthase in rats. Am. J. Physiol. --- Nitric oxide has been suggested to be an essential mediator of pressure natriuresis. To investigate this hypothesis, the effect of acute or chronic inhibition of nitric oxide synthase on pressure natriuresis and renal interstitial hydrostatic pressure was studied in anesthetized Sprague-Dawley rats with fixed neural and hormonal influences on the kidney. Both acute infusion (10 [mu]g x kg-1 x min-1, i.v.) and chronic administration (50 mg x kg-1 x day-1 for 7 days in drinking water) of NG-nitro-L-arginine methyl ester (L-NAME) resulted in significantly increased mean arterial pressure, a 30% decrease in renal blood flow, and no change in glomerular filtration rate when compared with values in control rats. Pressure-diuresis, pressure -natriuresis, and pressure-fractional sodium excretion curves in L -NAME-treated rats were shifted to a higher pressure (by about 25 mm Hg) when compared with those in control rats. The relationship between renal artery pressure and renal interstitial hydrostatic pressure was shifted similarly in L-NAME-treated rats. Acute administration of L-arginine completely reversed the renal effects of chronic L-NAME. These data indicate that at the doses used in this study, both acute and chronic inhibition of nitric oxide synthase decreased the ability of the kidney to excrete sodium at least in part by a hemodynamic mechanism leading to an increased filtration fraction and a decreased renal interstitial pressure. The parallel shift of the pressure-natriuresis curve to a higher pressure suggests that nitric oxide is an important modulator, but not an essential mediator of the pressure natriuresis. 

Received 23 March 1995; accepted in final form 15 August 1995.
APS Manuscript Number R194-5.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 24 August 1995.