The aim of this study was to investigate the influence of the mean level and phasic modulation of NO on the dynamic autoregulation of renal blood flow (RBF). Transfer functions were calculated from spontaneous fluctuations of RBF and arterial pressure (AP) in conscious resting dogs for 2 h under control conditions, after NO synthase (NOS) inhibition [N^G-nitro-L-arginine methyl ester hydrochloride (L-NAME)] and after L-NAME followed by a continuous infusion of an NO donor [S-nitroso-N-acetyl-DL-penicillamine (SNAP)]. After L-NAME (n = 7) AP was elevated, heart rate (HR) and RBF were reduced. The gain of the transfer function above 0.08 Hz was increased, compatible with enhanced resonance of the myogenic response. A peak of high gain around 0.03 Hz, reflecting oscillations of the tubuloglomerular feedback (TGF), was not affected. The gain below 0.01 Hz, was elevated, but still less than 0 dB, indicating diminished but not abolished autoregulation. After L-NAME and SNAP (n = 5), mean AP and RBF were not changed, but HR was slightly elevated. The gain above 0.08 Hz and the peak of high gain at 0.03 Hz were not affected. The gain below 0.01 Hz was elevated, but smaller than 0 dB. It is concluded that NO may help to prevent resonance of the myogenic response depending on the mean level of NO. The feedback oscillations of the TGF are not affected by NO. NO contributes to the autoregulation below 0.01 Hz due to phasic modulation independent of its mean level.

renal hemodynamics; transfer function; tubuloglomerular feedback; myogenic response; nitric oxide donor

This article has been cited by other articles:

				C. Lau, I. Sudbury, M. Thomson, P. L. Howard, A. B. Magil, and W. A. Cupples Salt-resistant blood pressure and salt-sensitive renal autoregulation in chronic streptozotocin diabetes Am J Physiol Regulatory Integrative Comp Physiol, June 1, 2009; 296(6): R1761 - R1770. [Abstract] [Full Text] [PDF]

				O. V. Sosnovtseva, A. N. Pavlov, E. Mosekilde, K.-P. Yip, N.-H. Holstein-Rathlou, and D. J. Marsh Synchronization among mechanisms of renal autoregulation is reduced in hypertensive rats Am J Physiol Renal Physiol, November 1, 2007; 293(5): F1545 - F1555. [Abstract] [Full Text] [PDF]

				X. Wang, R. D. Loutzenhiser, and W. A. Cupples Frequency modulation of renal myogenic autoregulation by perfusion pressure Am J Physiol Regulatory Integrative Comp Physiol, September 1, 2007; 293(3): R1199 - R1204. [Abstract] [Full Text] [PDF]

				W. A. Cupples and B. Braam Assessment of renal autoregulation Am J Physiol Renal Physiol, April 1, 2007; 292(4): F1105 - F1123. [Abstract] [Full Text] [PDF]

				A. Just Mechanisms of renal blood flow autoregulation: dynamics and contributions Am J Physiol Regulatory Integrative Comp Physiol, January 1, 2007; 292(1): R1 - R17. [Abstract] [Full Text] [PDF]

				Y. Shi, C. Lau, and W. A. Cupples Interactive modulation of renal myogenic autoregulation by nitric oxide and endothelin acting through ET-B receptors Am J Physiol Regulatory Integrative Comp Physiol, January 1, 2007; 292(1): R354 - R361. [Abstract] [Full Text] [PDF]

				Y. Shi, X. Wang, K. H. Chon, and W. A. Cupples Tubuloglomerular feedback-dependent modulation of renal myogenic autoregulation by nitric oxide Am J Physiol Regulatory Integrative Comp Physiol, April 1, 2006; 290(4): R982 - R991. [Abstract] [Full Text] [PDF]

				T. Wronski, E. Seeliger, P. B. Persson, C. Forner, C. Fichtner, J. Scheller, and B. Flemming The step response: a method to characterize mechanisms of renal blood flow autoregulation Am J Physiol Renal Physiol, October 1, 2003; 285(4): F758 - F764. [Abstract] [Full Text] [PDF]

				S. Racasan, J. A. Joles, P. Boer, H. A. Koomans, and B. Braam NO dependency of RBF and autoregulation in the spontaneously hypertensive rat Am J Physiol Renal Physiol, July 1, 2003; 285(1): F105 - F112. [Abstract] [Full Text] [PDF]

				V. Valdes, M. Mosqueira, S. Rey, R. Del Rio, and R. Iturriaga Inhibitory effects of NO on carotid body: contribution of neural and endothelial nitric oxide synthase isoforms Am J Physiol Lung Cell Mol Physiol, January 1, 2003; 284(1): L57 - L68. [Abstract] [Full Text] [PDF]

				M. R. Edwards, J. K. Shoemaker, and R. L. Hughson Dynamic modulation of cerebrovascular resistance as an index of autoregulation under tilt and controlled PETCO2 Am J Physiol Regulatory Integrative Comp Physiol, September 1, 2002; 283(3): R653 - R662. [Abstract] [Full Text] [PDF]

				A. Just, H. Ehmke, L. Toktomambetova, and H. R. Kirchheim Dynamic characteristics and underlying mechanisms of renal blood flow autoregulation in the conscious dog Am J Physiol Renal Physiol, June 1, 2001; 280(6): F1062 - F1071. [Abstract] [Full Text] [PDF]