Human aortic smooth muscle cells containing angiotensin II type 1 receptors

We characterized the angiotensin II (AII) receptor in human aortic smooth muscle cells (HASMCs). This receptor binds [125I]Sar1,Ile8-angiotensin II with a high affinity of 0.20 +/- 0.04 nM and a low capacity of 5.3 +/- 0.4 fmol/mg protein (230 +/- 17 sites/cell). Based on the Ki values, the ranking order of [125I]Sar1,Ile8-AII binding inhibition was as follows: Sar1,Ile8-AII > AII > Dup 753 > AII > AI >> PD 123319. The addition of AII to HASMCs induced a rapid, transient increase in intracellular free Ca2+ concentration followed by a lower, sustained phase. When extracellular Ca2+ was removed by adding 3 mM EGTA, this initial transient increase was not changed, but the sustained phase was abolished. These results revealed AII receptors in HASMCs to be of the type 1 receptor subtype, which induce Ca2+ mobilization mainly from intracellular Ca2+ stores.