title: Angiotensin II and cardiovascular regulation in a freshwater teleost, Anguilla rostrata LeSueur.
abstract: 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 [Asn1,Val5]angiotensin II (ANG II; 25-150 ng/kg iv) 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 the pressor effect of ANG II (100 ng/kg) primarily by attenuating the increase in blood flow (50-70%). The data provide evidence for an ANG II-mediated cardiovascular control in teleosts directly and indirectly via catecholamine release.
authors.affiliation: Department of Zoology, University of Toronto, Ontario, Canada.
authors.forename: G Y
authors.initials: GY
authors.lastname: Oudit
authors.forename: D G
authors.initials: DG
authors.lastname: Butler
mesh_terms: D018663:Adrenergic Agents / Q000494:pharmacology; D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D000319:Adrenergic beta-Antagonists / Q000494:pharmacology; D000804:Angiotensin II / Q000494:pharmacology / Q000502:physiology*; D000818:Animals; D001775:Blood Circulation / Q000187:drug effects; D001794:Blood Pressure / Q000187:drug effects; D002320:Cardiovascular Physiological Phenomena; D018678:Cholinergic Agents / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004524:Eels; D005260:Female; D005399:Fishes / Q000502:physiology*; D006339:Heart Rate / Q000187:drug effects; D012146:Rest
chemical_list: D018663:Adrenergic Agents; D000317:Adrenergic alpha-Antagonists; D000319:Adrenergic beta-Antagonists; D018678:Cholinergic Agents; D000804:Angiotensin II