Tonic and phasic influences of nitric oxide on renal blood flow
autoregulation in the conscious dog..
Just, Armin, Heimo Ehmke, Uwe Wittmann, Hartmut R. Kirchheim.
I._Physiologisches Institut, Ruprecht-Karls-Universit[umlaut]at
Heidelberg, D-69120 Heidelberg
APStracts 5:0211F, 1998.
The aim was to investigate the influence of the mean level and of
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 inhibition
(L_NAME) and after L_NAME followed by a continuous infusion of an NO
-donor (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, 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.
Received 17 August 1998; accepted in final form 30 November 1998.
APS Manuscript Number F210-8.
Article publication pending Am. J. Physiol. (Renal Physiology).
ISSN 1080-4757 Copyright 1998 The American Physiological Society.
Published in APStracts on 9 December 1998