Cardiovascular actions of angiotensin in the fowl (Gallus domesticus). II. Angiotensin analog agonists and antagonists.

Like angiotensin II (AII) itself, [SAR1] AII induced a biphasic blood pressure response in the conscious chicken--an initial depressor response followed by a pressor response. Angiotensin III, however, induced only a depressor response in the dose range tested. The response to angiotensin I was similar to that to AII, and appeared to be due to its conversion to AII as it was inhibited by prior infusion of the angiotensin converting enzyme inhibitor SQ 20,881. Two angiotensin analog antagonists [SAR1ALA8] AII and [SAR1ILE8] AII inhibited both components of the response to AII, but the pressor response was inhibited at lower concentrations of antagonist than was the depressor response. These findings give further support to the suggestion that the pressor and depressor component of the response to AII in the conscious chicken are mediated via different AII receptors, and indicate the possibility of selective blockade of these two components.