Paci A, Cocci F, Piras F, Niedermeyer H P, Matteucci E, Vitali C, Ciarimboli G, Bombardieri S
J Nucl Med Allied Sci. 1989 Jan-Mar;33(1):15-21.
The highly specific beta-adrenergic radioligand (-)[125I]iodocyanopindolol (ICYP) was used to characterize the beta-adrenergic receptor subtype present in human placenta. Binding of ICYP to membranes from human placenta was saturable with time and ligand concentration, of high affinity, and demonstrated appropriate stereoselectivity and agonist rank order of potency for binding to a beta-adrenergic receptor. From saturation binding curves, the KD and Bmax values for ICYP binding were 233 +/- 51 pM and 690 +/- 139 fmol/mg of proteins, respectively. Analysis of inhibition of ICYP binding by beta 1- and beta 2-selective adrenergic antagonists via Hofstee analysis resulted in linear plots, indicating the existence of a homogeneous population of beta-adrenergic receptors. From the resulting KI-values for the beta 1-selective drugs practolol (4.0 +/- 0.9 microM) and metoprolol (0.19 +/- 0.07 microM) and for the beta 2-selective drug ICI 118,551 (0.30 +/- 0.06 microM) it is concluded that the beta-adrenergic receptor in human placenta is of the beta 1-subtype. This is further supported by the fact that (-)-noradrenaline and (-)-adrenaline were equipotent in inhibiting ICYP binding.
高特异性的β-肾上腺素能放射性配体（-）-[¹²⁵I]碘氰吲哚洛尔（ICYP）被用于鉴定人胎盘中存在的β-肾上腺素能受体亚型。ICYP与人胎盘膜的结合随时间和配体浓度达到饱和，具有高亲和力，并表现出适当的立体选择性和激动剂结合β-肾上腺素能受体的效价顺序。根据饱和结合曲线，ICYP结合的KD和Bmax值分别为233±51 pM和690±139 fmol/mg蛋白质。通过霍夫斯泰分析对β1和β2选择性肾上腺素能拮抗剂抑制ICYP结合的分析产生了线性图，表明存在均匀的β-肾上腺素能受体群体。根据β1选择性药物心得宁（4.0±0.9 microM）和美托洛尔（0.19±0.07 microM）以及β2选择性药物ICI 118,551（0.30±0.06 microM）的所得KI值，可以得出结论，人胎盘中的β-肾上腺素能受体是β1亚型。（-）-去甲肾上腺素和（-）-肾上腺素在抑制ICYP结合方面等效这一事实进一步支持了这一点。
