Shibata K, Foglar R, Horie K, Obika K, Sakamoto A, Ogawa S, Tsujimoto G
Department of Molecular and Cell Pharmacology, National Children's Medical Research Center, Tokyo, Japan.
Mol Pharmacol. 1995 Aug;48(2):250-8.
alpha 1-Adrenoceptors (ARs) comprise a heterogeneous family, and subtype-selective ligands are valuable for studying the functional role of each receptor subtype. We characterized a newly synthesized, alpha 1-AR antagonist, KMD-3213, by using Chinese hamster ovary cells stably expressing the three cloned human alpha 1-ARs (alpha 1a, alpha 1b, and alpha 1d), as well as native rat and human tissues. KMD-3213 potently inhibited 2-[2-(4-hydroxy-3-[125I]iodophenyl)ethylaminomethyl]-alpha-tetralone binding to the cloned human alpha 1a-AR, with a Ki value of 0.036 nM, but had 583- and 56-fold lower potency at the alpha 1b- and alpha 1d-ARs, respectively. KMD-3213 inhibited norepinephrine-induced increases in intracellular Ca2+ concentrations in alpha 1a-AR-expressing Chinese hamster ovary cells with an IC50 of 0.32 nM but had a much weaker inhibitory effect on the alpha 1b- and alpha 1d-ARs. Using pharmacologically well characterized native rat tissues [submaxillary gland (alpha 1A-AR-expressing tissue), liver (alpha 1B-AR-expressing tissue), and heart (mixed alpha 1A- and alpha 1B-AR-expressing tissue)], binding studies showed that inhibition curves for KMD-3213 in submaxillary gland and liver best fit a one-site model (with Ki values of 0.15 and 16 nM, respectively), whereas KMD-3213 had high and low affinity sites in heart membranes. Chloroethylclonidine treatment of rat heart membranes completely eliminated the low affinity sites for KMD-3213. Furthermore, in human liver and prostate KMD-3213 could identify high and low affinity sites, the Ki values of which corresponded well to those for the cloned human alpha 1a- and alpha 1b-ARs, respectively. Moreover, the affinity of KMD-3213 was found to be approximately 10-fold higher at the cloned human alpha 1a-AR than at the cloned rat alpha 1a-AR. KMD-3213 is a potent and highly selective antagonist for the human alpha 1a-AR and would be useful for studying the physiological roles of human alpha 1-AR subtypes.
α1肾上腺素能受体（ARs）构成一个异质性家族，亚型选择性配体对于研究每种受体亚型的功能作用很有价值。我们通过使用稳定表达三种克隆的人α1-ARs（α1a、α1b和α1d）的中国仓鼠卵巢细胞以及天然大鼠和人体组织，对一种新合成的α1-AR拮抗剂KMD-3213进行了特性分析。KMD-3213能有效抑制2-[2-(4-羟基-3-[125I]碘苯基)乙氨基甲基]-α-四氢萘酮与克隆的人α1a-AR的结合，Ki值为0.036 nM，但对α1b-AR和α1d-AR的效力分别低583倍和56倍。KMD-3213抑制去甲肾上腺素诱导的表达α1a-AR的中国仓鼠卵巢细胞内Ca2+浓度升高，IC50为0.32 nM，但对α1b-AR和α1d-AR的抑制作用弱得多。利用药理学特性明确的天然大鼠组织[颌下腺（表达α1A-AR的组织）、肝脏（表达α1B-AR的组织）和心脏（表达α1A-AR和α1B-AR的混合组织）]进行结合研究表明，KMD-3213在颌下腺和肝脏的抑制曲线最符合单点模型（Ki值分别为0.15和16 nM），而KMD-3213在心脏膜中有高亲和力和低亲和力位点。用氯乙可乐定处理大鼠心脏膜可完全消除KMD-3213的低亲和力位点。此外，在人肝脏和前列腺中，KMD-3213可识别高亲和力和低亲和力位点，其Ki值分别与克隆的人α1a-AR和α1b-AR的Ki值非常吻合。而且，发现KMD-3213对克隆的人α1a-AR的亲和力比对克隆的大鼠α1a-AR高约10倍。KMD-3213是一种对人α1a-AR有效的高选择性拮抗剂，可用于研究人α1-AR亚型的生理作用。
