Cardiac output mediates the antihypertensive effect of vasopressin
in spontaneous hypertension.
Balakrishnan, Suchitra, and J. Robert McNeill.
Department of Pharmacology, College of Medicine, University of
Saskatchewan, Saskatoon, Sk. Canada, S7N 5E5
APStracts 3:0124H, 1996.
The contribution of cardiac output and total peripheral resistance to
the fall in arterial pressure that follows cessation of a 3 hr
intravenous infusion of arginine vasopressin (AVP; 20 ng/kg/min) was
studied in conscious spontaneously hypertensive rats (SHR) and
Wistar-Kyoto rats (WKY) instrumented with radiotelemetric probes for
recording of blood pressure and ultrasonic transit-time flow probes
for measuring cardiac output. Cessation of a three hour infusion of
AVP resulted in a significant decrease in arterial pressure in SHR
(14-17 mm Hg below pre-infusion control levels) but not in WKY nor in
vehicle treated controls. The fall in pressure persisted for several
days. The fall in pressure was associated with a large decrease in
cardiac output of 22 +/- 2 ml/minute below control levels in SHR, and
the time course of the cardiac output response over several days
approximated the time-course of the pressure response. By contrast,
total peripheral resistance remained elevated for some time on
withdrawal of the AVP infusion. We conclude that the WAP in SHR is
mediated by a fall in cardiac output and not by a decline in total
peripheral resistance.
Received 18 July 1995; accepted in final form 14 March 1996.
APS Manuscript Number H673-5.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 1 April 96