Bovine Aortic Endothelial Cells Contain an Angiotensin-(1–7) Receptor

Abstract

Angiotensin-(1–7) is a novel peptide of the reninangiotensin system that counteracts the pressor and proliferative responses to angiotensin II. We now report that cultured bovine aortic endothelial cells contain a saturable, high-affinity [ ¹²⁵ I]angiotensin-(1–7) binding site with an affinity of 19.3±10.7 nmol/L and a density of 1351±710 fmol/mg protein. Angiotensin-(1–7) competed at a second lower-affinity site, with an IC ₅₀ of 2.9 μmol/L. The high-affinity angiotensin II receptor antagonist sarcosine ¹ -isoleucine ⁸ -angiotensin II blocked [ ¹²⁵ I]angiotensin-(1–7) binding to bovine aortic endothelial cells at both a high-(IC ₅₀ =1.3 nmol/L) and a low-affinity (IC ₅₀ =6.2 μmol/L) binding site. In contrast, d -alanine ⁷ -angiotensin-(1–7) completely blocked [ ¹²⁵ I]angiotensin-(1–7) binding, with an IC ₅₀ of 19.8 nmol/L, suggesting that d -alanine ⁷ -angiotensin-(1–7) may selectively block responses to angiotensin-(1–7) in endothelial cells. Neither the AT ₁ antagonist losartan nor the AT ₂ antagonist PD 123319 exhibited significant competition for [ ¹²⁵ I]angiotensin-(1–7) binding to endothelial cells isolated from bovine aorta, in agreement with the absence of detectable mRNAs encoding typical angiotensin receptor subtypes 1 or 2 (AT ₁ or AT ₂ ). Angiotensin II also competed for [ ¹²⁵ I]angiotensin-(1–7) binding to bovine aortic endothelial cells; however, the relative affinity was 13-fold lower than angiotensin-(1–7), suggesting a preference for angiotensin-(1–7) over angiotensin II. These results demonstrate that bovine aortic endothelial cells contain a unique non-AT ₁ , non-AT ₂ angiotensin receptor that preferentially binds angiotensin-(1–7).