Frequency domain of renal autoregulation in the conscious dog.
Wittmann, Uwe, Benno Nafz, Heimo Ehmke, Hartmut R. Kirchheim, and
Pontus B. Persson.
I. Physiologisches Institut der Ruprecht-Karls Universit[umlaut]at
Heidelberg, Germany, Physiologisches Institut der Charit[acute]e,
Humboldt Universit[umlaut]at Berlin, Germany
APStracts 2:0047F, 1995.
The dynamic range in which renal blood flow (RBF) autoregulation
occurs was determined in 8 conscious foxhounds chronically
instrumented with catheters in the abdominal aorta and a transit time
flowprobe implanted over the renal artery. Sinusoidal driving
pressures (amplitude of 10 mmHg) were forced upon the renal arterial
pressure at different frequencies by a servo-control device and
transfer functions were calculated. Only one frequency range was
found below which the gain of the transfer function declined and in
which the phase angle increased (N = 8). This indicates the presence
of a potent mechanism for renal autoregulation in the examined
frequency range between 0.0031 Hz and 0.08 Hz which buffers changes
in blood flow below 0.02 Hz. After furosemide treatment, one
indicator for autoregulation (phase shift of transfer function) was
significantly blunted at low frequencies (N = 6). Furosemide,
however, did not reduce the phase shift to zero suggesting that some
autoregulation still remained in the frequency range between 0.04 Hz
and 0.08 Hz. In conclusion, autoregulation of RBF during sinusoidal
changes in driving pressure between 0.0031 Hz and 0.02 Hz is mediated
by a single mechanism which can be blocked by the acute
administration of furosemide. The residual phase shift between AP and
RBF in the transfer function observed during sinusoidal changes in
driving pressure between 0.04 Hz and 0.08 Hz suggests the presence of
a second mechanism for RBF autoregulation.
Received 24 April 1994; accepted in final form 6 March 1995.
APS Manuscript Number F172-4.
Article publication pending Am. J. Physiol. (Renal Fluid Electrolyte
Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 10 April 1995.