Angiotensin ii and cardiovascular regulation in a freshwater
teleost, anguilla rostrata lesueur.
Oudit, Gavin Y., and David G. Butler.
Department of Zoology, 25 Harbord St., University of Toronto,
Toronto, Ontario, M5S 1A1, Canada, Telephone #: 416-978-3503, Fax #:
416-978-8532
APStracts 2:0112R, 1995.
Cardiac output (CO), dorsal aortic blood flow (BFDA) and blood
pressure (PDA), and heart rate (HR) were recorded simultaneously in
conscious freshwater eels. Physiological doses of [Asn1Val5]-ANG II
(25-150 ng kg-1 i.v.) were used to investigate its effects on the
blood flow (CO, BFDA and estimated branchial shunting (BS)) and
systemic vascular resistance (RSYS) components of the pressor
response and possible mechanism(s) of action. CO was increased mainly
by an elevated stroke volume (SV) due to positive inotropy and/or
Frank-Starling principle in a dose-related manner. An intact
baroreceptor reflex attenuated the blood flow increase by 25% via the
inhibitory cardiac vagal innervation. The elevation in estimated BS
was a passive response to the increased CO since the proportion of CO
perfusing the pathway remained constant. PDA showed a similar dose
-dependent increase in response to ANG II but the peak PDA preceded
the peak CO responses at all doses; RSYS was only transiently
elevated at peak PDA. The increase in blood flow was an important
contributor to the vasopressor responses. Alpha-adrenergic blockade
partially inhibited (50-70%) the pressor effect of ANG II (100 ng kg
-1) primarily by attenuating the increase in blood flow. The data
provides evidence for an ANG II-mediated cardiovascular control in
teleost, directly and indirectly via catecholamine release.
Received 22 November 1994; accepted in final form 12 April 1995.
APS Manuscript Number R680-4.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 2 May 1995.