Dynamic autoregulation in the in vitro perfused hydronephrotic rat
kidney.
Cupples, William A, and Rodger D Loutzenhiser.
Division of Nephrology and Lady Davis Institute, Sir Mortimer B.
Davis-Jewish General Hospital, Montreal, Quebec and Smooth Muscle
Research Group and Department of Pharmacology and Therapeutics,
University of Calgary, Calgary, Alberta Canada
APStracts 5:0082F, 1998.
Renal autoregulation is mediated by tubuloglomerular feedback,
operating at 0.03-0.05 Hz, and a faster system, operating at 0.1-0.2
Hz, that has been attributed by exclusion to myogenic
vasoconstriction. In this study, we examined dynamic autoregulation
in the hydronephrotic rat kidney which lacks tubuloglomerular
feedback, but exhibits pressure-induced afferent arteriolar
vasoconstriction. Kidneys were harvested under anesthesia from
Sprague-Dawley rats and perfused in vitro using defined, colloid-free
medium. Renal perfusate flow was assessed during forced pressure
fluctuations at mean pressures of 60 - 140 mmHg. Transfer function
analysis revealed passive behavior at 60 mmHg and active, pressure
-dependent responses at higher pressures. In all cases coherence was
high (0.89[angstrom]a0.03 between 0.01 and 0.9 Hz). There was a
resonance peak in admittance gain at [diaeresis]e0.3 Hz and an
associated broad peak in phase angle. Below this frequency, gain
declined progressively. The minimum gain achieved at 0.01 - 0.05 Hz
was pressure-sensitive, being 1.08[angstrom]a0.02 at 60 mmHg and
0.71[angstrom]a0.04 at 140 mmHg. These findings are consistent with
in vivo results and with model-based predictions of the dynamics of
myogenic autoregulation, supporting the postulate that the rapid
component of autoregulation reflects operation of a myogenic
mechanism.
Received 26 January 1998; accepted in final form 2 April 1998.
APS Manuscript Number F178-8.
Article publication pending Am. J. Physiol. (Renal Physiology).
ISSN 1080-4757 Copyright 1998 The American Physiological Society.
Published in APStracts on 24 April 1998