AJP - Heart and Circulatory Physiology, Vol 256, Issue 2 502-H507, Copyright © 1989 by American Physiological Society
Vascular capacitance and reversal of 2-kidney, 1-clip hypertension in rats
M. E. Edmunds, G. I. Russell and J. D. Swales
Department of Medicine, University of Leicester, United Kingdom.
Vascular capacitance was studied in conscious early-phase (less than 6 wk)
2-kidney, 1-clip (2K, 1C) hypertension and compared with sham-clipped
control rats. Two other groups of 2K, 1C rats were studied before and 6 h
after unclipping or a sham operation. Mean circulatory filling pressure
(MCFP) was measured during a brief circulatory arrest caused by inflation
of a right atrial balloon. Blood volume (BV) was determined from plasma
volume (125I-labeled albumin) and hematocrit. MCFP was measured at resting
BV and after rapid BV changes. Vascular compliance was derived from the
MCFP-BV curve. Hypertensive 2K, 1C rats had an increase in hematocrit (46
+/- 1.3 vs. 42 +/- 0.4%, P less than 0.01) and no difference in BV compared
with controls. MCFP was increased (8.6 +/- 1.0 vs. 7.2 +/- 0.2 mmHg, P less
than 0.01) with no difference in compliance, indicating decreased
unstressed vascular volume in the 2K, 1C group. After unclipping, there was
a significant fall in mean arterial pressure to normal, with a fall in MCFP
(8.14 +/- 0.32 to 6.78 +/- 0.11 mmHg, P less than 0.01), but there was no
difference in BV or compliance compared with the 2K, 1C group, indicating
an increase in unstressed vascular volume after unclipping. These studies
for the first time show an important role for vascular capacitance in
modulating the circulatory changes accompanying the fall in blood pressure
in surgical reversal of 2K, 1C hypertension.
