Murata S, Taniguchi T, Muramatsu I
Department of Pharmacology, School of Medicine, Fukui Medical University, Matsuoka, Japan.
Br J Pharmacol. 1999 May;127(1):19-26. doi: 10.1038/sj.bjp.0702489.
Pharmacological profiles of tritiated KMD-3213, a new antagonist of alpha1-adrenoceptor (AR), were examined in recombinant and native alpha1-AR, and compared with those of prazosin (PZ) and tamsulosin (YM-617). In saturation experiments, [3H]-KMD (10-2000 pM) showed high affinity for alpha1a-AR (pK(D) = 10.5). However, no significant binding to alpha1b-AR and insufficient/unsaturated binding to alpha1d-AR were observed at concentrations up to 2000 pM. In contrast, [3H]-PZ and [3H]-YM bound to all subtypes with high affinity (pK(D)>9). In competition experiments, KMD-3213 also had higher affinity for alpha1a-AR than for other two subtypes; pKi = 10.4, 8.1 and 8.6 for alpha1a-, alpha1b- and alpha1d-AR, respectively. [3H]-KMD also bound to the native alpha1A-AR (rat submaxillary gland) with high affinity, but not to alpha1B-AR (rat liver). In rat kidney which expresses alpha1A- and alpha1B-AR, [3H]-KMD and [3H]-PZ bound to a single high-affinity site (pK(D) = 10.8 and 10.1, respectively) with distinct amount of binding sites (Bmax = 159 and 267 fmol mg(-1) protein, respectively). [3H]-PZ binding sites consisted of low- and high-affinity sites for KMD-3213 (pKi = 7.6 and 10.7, respectively), for WB4101 (pK = 8.1 and 10.0) and for YM-617 (pKi = 8.7 and 10.8). The proportion of the high affinity site was approximately 60% in these drugs which was compatible to the ratio between Bmax of [3H]-KMD and [3H]-PZ. [3H]-KMD binding sites consisted of a single site for these drugs with affinities which were similar to those of the high affinity sites in [3H]-PZ binding. In functional experiments, KMD-3213 antagonized the contractile responses to NS-49 or noradrenaline (NA) with higher affinity in functional alpha1A- (rat caudal artery, pA2= 10.0 against NS-49) and alpha1L-AR (dog mesenteric artery, pA2 = 9.9 against NA) than in alpha1B- (dog carotid artery, pA2 = 7.7 against NA) and alpha1D-AR (rat thoracic aorta, pA2 = 8.3 against NA). These results confirm the alpha1A-AR selectivity and high affinity of KMD-3213, and indicate that [3H]-KMD can label selectively alpha1A-AR.
研究了新型α1肾上腺素能受体（AR）拮抗剂氚标记的KMD-3213在重组和天然α1-AR中的药理学特性，并与哌唑嗪（PZ）和坦索罗辛（YM-617）进行了比较。在饱和实验中，[3H]-KMD（10 - 2000 pM）对α1a-AR表现出高亲和力（pK(D)=10.5）。然而，在高达2000 pM的浓度下，未观察到与α1b-AR的显著结合，且与α1d-AR的结合不足/不饱和。相比之下，[3H]-PZ和[3H]-YM与所有亚型均具有高亲和力结合（pK(D)>9）。在竞争实验中，KMD-3213对α1a-AR的亲和力也高于其他两个亚型；α1a-、α1b-和α1d-AR的pKi分别为10.4、8.1和8.6。[3H]-KMD也以高亲和力与天然α1A-AR（大鼠颌下腺）结合，但不与α1B-AR（大鼠肝脏）结合。在表达α1A-和α1B-AR的大鼠肾脏中，[3H]-KMD和[3H]-PZ与单个高亲和力位点结合（pK(D)分别为10.8和10.1），结合位点数量不同（Bmax分别为159和267 fmol mg(-1)蛋白）。[3H]-PZ结合位点由对KMD-3213（pKi分别为7.6和10.7）、对WB4101（pK分别为8.1和10.0）以及对YM-617（pKi分别为8.7和10.8）的低亲和力和高亲和力位点组成。在这些药物中，高亲和力位点的比例约为60%，这与[3H]-KMD和[3H]-PZ的Bmax之比相符。[3H]-KMD结合位点由这些药物的单个位点组成，并具有与[3H]-PZ结合中的高亲和力位点相似的亲和力。在功能实验中，KMD-3213在功能性α1A-（大鼠尾动脉，对NS-49的pA2 = 10.0）和α1L-AR（犬肠系膜动脉，对去甲肾上腺素（NA）的pA2 = 9.9）中比在α1B-（犬颈动脉，对NA的pA2 = 7.7）和α1D-AR（大鼠胸主动脉，对NA的pA2 = 8.3）中以更高的亲和力拮抗对NS-49或去甲肾上腺素（NA）的收缩反应。这些结果证实了KMD-3213的α1A-AR选择性和高亲和力，并表明[3H]-KMD可选择性标记α1A-AR。
