The pressor response to exogenous angiotensin I and its blockade by angiotensin II analogues in the American alligator.
We examined the pressor response to exogenous, nonnative angiotensin I (ANG I; bullfrog, turtle, and fowl) in the conscious American alligator, Alligator mississippiensis. In addition, the inhibitory effects of three ANG II analogues ([Sar1, Ala8], [Sar1, Thr8], and [Sar1, Ile8]ANG II) on the pressor responses to angiotensin I (fowl ANG I, [Asp1, Val5, Ser9]) were also examined. Intravenous administration of bullfrog, turtle, and fowl ANG I at 0.1, 0.5, and 1.0 micrograms/kg produced dose-dependent increases in arterial blood pressure. [Val5]ANG II at 0.05, 0.1, and 0.5 micrograms/kg, or NE at 2 micrograms/kg also produced dose-dependent increases in blood pressure. [Sar1, Ile8]ANG II and [Sar1, Ala8]ANG II (10 micrograms/kg/min) both attenuated the pressor response to fowl ANG I whereas [Sar1, Thr8]ANG II (10 micrograms/kg/min) produced no significant blockade. These data demonstrate: (1) All three exogenous ANG I molecules exert potent vasopressor responses in the alligator, (2) [Sar1, Ile8]ANG II is the most effective ANG antagonist, and (3) the alligator appears to possess a renin-angiotensin system similar to that found in other vertebrates.
Silldorff
E P
EP
School of Life and Health Sciences, University of Delaware, Newark 19716.
Stephens
G A
GA
D015059:1-Sarcosine-8-Isoleucine Angiotensin II / Q000494:pharmacology; D000489:Alligators and Crocodiles / Q000502:physiology*; D000803:Angiotensin I / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D000804:Angiotensin II / Q000031:analogs & derivatives* / Q000494:pharmacology; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D007275:Injections, Intravenous; D009638:Norepinephrine / Q000494:pharmacology; D012504:Saralasin / Q000494:pharmacology
D000804:Angiotensin II; C014805:angiotensin II, Sar(1)-Thr(8)-; D000803:Angiotensin I; D015059:1-Sarcosine-8-Isoleucine Angiotensin II; D012504:Saralasin; D009638:Norepinephrine