A Single β-Amino Acid Substitution to Angiotensin II Confers AT2 Receptor Selectivity and Vascular Function

Novel AT2R ligands were designed by substituting individual β-amino acid in the sequence of the native ligand angiotensin II (Ang II). Relative ATR selectivity and functional vascular assays (in vitro AT2R-mediated vasorelaxation and in vivo vasodepressor action) were determined. In competition binding experiments using either AT1R- or AT2R- transfected HEK-293 cells, only β-Asp-Ang II and Ang II fully displaced [I]-Ang II from AT1R. In contrast, β-substitutions at each position of Ang II exhibited AT2R affinity, with β-Tyr-Ang II and β-Ile-Ang II exhibiting ≈1000-fold AT2R selectivity. In mouse aortic rings, β-Tyr-Ang II and β-Ile-Ang II evoked vasorelaxation that was sensitive to blockade by the AT2R antagonist PD123319 and the nitric oxide synthase inhibitor L-NAME. When tested with a low level of AT1R blockade, β-Ile-Ang II (15 pmol/kg per minute IV for 4 hours) reduced blood pressure (BP) in conscious spontaneously hypertensive rats (β-Ile-Ang II plus candesartan, −24±4 mm Hg) to a greater extent than candesartan alone (−11±3 mm Hg, n=7, P