Angiotensin(1-7) is an antagonist at the type 1 angiotensin II receptor.
OBJECTIVE
The present study investigated the antagonism of the amino-terminal heptapeptide fragment of angiotensin II ([des-Phe8]-angiotensin II; Ang(1-7)) to angiotensin II (Ang II) both in vitro in rabbit aortae and in vivo in rats.


RESULTS
In rabbit isolated endothelium intact aortic rings Ang(1-7) caused a concentration-related rightward displacement of the Ang II curve and depressed the maximum response to Ang II. By applying the data to a Schild plot an apparent pA2 of 5.5 was calculated. This depression of maximum response could be reversed by co-incubation of Ang(1-7) with the competitive angiotensin antagonist losartan. Ang(1-7) had no effect on the contractile responses of several other agonists. Intravenous infusion of 10 or 100 micrograms/kg per min Ang(1-7) had no effect on the resting blood pressure in the anaesthetized rat but inhibited Ang II-induced pressor responses.


CONCLUSIONS
The present results show that Ang(1-7) is a specific non-competitive antagonist of Ang II at type 1 angiotensin II receptors.
Mahon
J M
JM
Institute of Endocrinology, University of Sheffield, UK.
Carr
R D
RD
Nicol
A K
AK
Henderson
I W
IW
D000803:Angiotensin I; D000804:Angiotensin II / Q000037:antagonists & inhibitors* / Q000494:pharmacology*; D057911:Angiotensin Receptor Antagonists; D000818:Animals; D001713:Biphenyl Compounds / Q000494:pharmacology; D001794:Blood Pressure / Q000187:drug effects; D007093:Imidazoles / Q000494:pharmacology; D066298:In Vitro Techniques; D019808:Losartan; D008297:Male; D010446:Peptide Fragments / Q000494:pharmacology*; D011817:Rabbits; D051381:Rats; D017207:Rats, Sprague-Dawley; D013777:Tetrazoles / Q000494:pharmacology
D057911:Angiotensin Receptor Antagonists; D001713:Biphenyl Compounds; D007093:Imidazoles; D010446:Peptide Fragments; D013777:Tetrazoles; D000804:Angiotensin II; D000803:Angiotensin I; C118790:angiotensin I (1-7); D019808:Losartan