Angiotensin II: dependence of hormone affinity on the electronegativity of a single side chain

Abstract
Structure-activity studies on rabbit aorta of angiotensin II anlaogs have suggested a possible relationship between the electronegativity of the aromatic side chain in position 4 (Tyr) and the observed affinity. To test this hypothesis, several other anlogs modified in position 4 were prepared, and all available analogs were tested in 3 bioassays: in vitro on rabbit aorta strip, in vivo on the rat blood pressure, and the the binding assay on beef adrenocortical membranes. In all 3 bioassays the postulated correlation confirmed that angiotensin II affinity depends inversely on the electronegativity of the aromatic side chain in position 4.