Bovine aortic endothelial cells contain an angiotensin-(1-7) receptor

Abstract

Angiotensin-(1-7) is a novel peptide of the renin-angiotensin 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 [125I]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 IC50 of 2.9 μmol/L. The high-affinity angiotensin II receptor antagonist sarcosine1-isoleucine8-angiotensin II blocked [125I]angiotensin (1-7) binding to bovine aortic endothelial cells at both a high- (IC50=1.3 nmol/L) and a low-affinity (IC50=6.2 μmol/L) binding site. In contrast, D- alanine7-angiotensin-(1-7)completely blocked [125I]angiotensin-(1-7) binding, with an IC50 of 19.8 nmol/L, suggesting that D-alanine7- angiotensin-(1-7) may selectively block responses to angiotensin-(1-7) in endothelial cells. Neither the AT1 antagonist losartan nor the AT2 antagonist PD 123319 exhibited significant competition for [125I]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 (AT1 or AT2). Angiotensin II also competed for [125I]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-AT1, non-AT2 angiotensin receptor that preferentially binds angiotensin-(1-7).