Moore G J, Kwok Y C
Life Sci. 1987 Jul 27;41(4):505-11. doi: 10.1016/0024-3205(87)90228-1.
Angiotensin receptors in rat uterine smooth muscle have been investigated by [125I]angiotensin II binding studies in membrane preparations. Scatchard analysis of binding data has demonstrated the presence of low and high affinity angiotensin binding sites with KLD = 3.0 X 10(-8) and KHD = 5.0 X 10(-10)M respectively. These values are identical to our previously reported values for the EC50 and dissociation constant, respectively, obtained from bioassays on intact uterine tissues. The antagonist [Sar1, Ile8]angiotensin II also demonstrates a binding affinity in uterine membranes (pKD = 8.7) which is not significantly different from its apparent binding affinity (pA2 = 8.6) in responding tissues. Taken in conjunction with our previously published bioassay data the present binding studies suggest that the resting state of the angiotensin receptor in smooth muscle is a low affinity state, and that interaction with ANG II induces a portion of the receptors into a high affinity "excited" state. The antagonist [Sar1, Ile8]angiotensin II apparently binds with higher affinity than angiotensin II to the low affinity (resting) state of the receptor.
通过对大鼠子宫平滑肌膜制剂进行[125I]血管紧张素II结合研究，对其中的血管紧张素受体进行了研究。对结合数据的Scatchard分析表明，存在低亲和力和高亲和力的血管紧张素结合位点，其解离常数分别为KLD = 3.0×10(-8)和KHD = 5.0×10(-10)M。这些值分别与我们之前报道的从完整子宫组织生物测定中获得的EC50和解离常数的值相同。拮抗剂[Sar1，Ile8]血管紧张素II在子宫膜中也表现出结合亲和力（pKD = 8.7），与其在反应组织中的表观结合亲和力（pA2 = 8.6）无显著差异。结合我们之前发表的生物测定数据，目前的结合研究表明，平滑肌中血管紧张素受体的静息状态是低亲和力状态，与血管紧张素II的相互作用会诱导一部分受体进入高亲和力的“激活”状态。拮抗剂[Sar1，Ile8]血管紧张素II与受体的低亲和力（静息）状态结合时，其亲和力明显高于血管紧张素II。
