Kelly Curtis R, Sharif Najam A
Molecular Pharmacology (R2-43), Alcon Research, Ltd., 6201 South Freeway, Fort Worth, TX 76134, USA.
J Pharmacol Exp Ther. 2006 Jun;317(3):1254-61. doi: 10.1124/jpet.105.100172. Epub 2006 Mar 3.
The present study investigated the serotonin-induced increase in phosphoinositide hydrolysis and mobilization of intracellular Ca2+ ([Ca2+]i) in human uterine smooth muscle cells (HUSMCs) to identify the serotonergic receptor positively coupled to phospholipase C in these cells. In phosphoinositide (PI) assays, serotonin (5-HT) and alpha-methyl-5-HT were potent, full agonists (EC50 = 20 and 4.1 nM, respectively), whereas the phenylethylamine, R-(-)-1-(4-iodo-2,5-dimethoxyphenyl)-2-aminopropane hydrochloride, was less active (EC50 = 63 nM). Proposed 5-HT2B-selective agonists, BW-723C86 [alpha-methyl-5-(2-thienylmethoxy)-1H-indole-3-ethanamine hydrochloride] and (+)-norfenfluramine, exhibited strong agonist potency and efficacy comparable with 5-HT (EC50 = 18 and 33 nM, respectively) and approximately 15-fold more potency than (-)-norfenfluramine (EC50 = 500 nM). 5-HT2C receptor agonists m-chlorophenylpiperazine and MK-212 [6-chloro-2-(1-piperaxinyl)pyrazine] were weak agonists in these cells, with potencies of 110 and 880 nM, respectively. A similar rank order of potency was observed in [Ca2+]i mobilization assays (r = 0.9, p < 0.005) in the HUSMC and with contraction of rat stomach fundus strips that contain a 5-HT2B receptor (r = 0.9, p < 0.001). Antagonist studies revealed that a 5-HT2B-selective antagonist, RS-127445 [2-amino-4-(4-fluoronaphth-1-yl)-6-isopropylpyrimidine] (Ki = 0.13 nM), was significantly more effective at inhibiting 5-HT-induced activity than a 5-HT2A antagonist, M-100907 (R-(+)-alpha-(2,3-dimethoxyphenyl)-1-[2-(4-fluorophenyl)ethyl]-4-piperidinemethanol]) (Ki= 914 nM) and the 5-HT2C antagonists RS-102221 (8-[5-(2,4-dimethoxy-5-(4-trifluoromethylsulfo-amido)phenyl-5-oxopentyl]-1,3,8-triazaspiro[4.5]decane-2,4-dione hydrochloride) (Ki = 2.5 microM) and SB-242084 (6-chloro-5-methyl-1-[6-92-methylpyridin-3-yloxy) pyridine-3-ylcarbamoyl] indoline) (Ki = 42.4 nM) in the HUSMC PI turnover assays. Taken together, these studies strongly suggest the presence of a functionally active 5-HT2B receptor subtype in HUSMCs. The physiological role of this receptor in these cells remains to be defined.
本研究调查了血清素诱导人子宫平滑肌细胞（HUSMCs）中磷酸肌醇水解增加及细胞内Ca2+（[Ca2+]i）动员的情况，以确定在这些细胞中与磷脂酶C正性偶联的血清素能受体。在磷酸肌醇（PI）分析中，血清素（5-HT）和α-甲基-5-HT是强效的完全激动剂（EC50分别为20和4.1 nM），而苯乙胺R-(-)-1-(4-碘-2,5-二甲氧基苯基)-2-氨基丙烷盐酸盐活性较低（EC50 = 63 nM）。拟5-HT2B选择性激动剂BW-723C86 [α-甲基-5-(2-噻吩基甲氧基)-1H-吲哚-3-乙胺盐酸盐]和(+)-去甲氟西汀表现出与5-HT相当的强激动剂效力和效能（EC50分别为18和33 nM），且效力比(-)-去甲氟西汀（EC50 = 500 nM）高约15倍。5-HT2C受体激动剂间氯苯哌嗪和MK-212 [6-氯-2-(1-哌嗪基)吡嗪]在这些细胞中是弱激动剂，效力分别为110和880 nM。在HUSMCs的[Ca2+]i动员分析（r = 0.9，p < 0.005）以及含有5-HT2B受体的大鼠胃底条收缩实验（r = 0.9，p < 0.001）中观察到了类似的效力排序。拮抗剂研究表明，5-HT2B选择性拮抗剂RS-127445 [2-氨基-4-(4-氟萘-1-基)-6-异丙基嘧啶]（Ki = 0.13 nM）在抑制5-HT诱导的活性方面比5-HT2A拮抗剂M-100907（R-(+)-α-(2,3-二甲氧基苯基)-1-[2-(4-氟苯基)乙基]-4-哌啶甲醇]）（Ki = 914 nM）以及5-HT2C拮抗剂RS-102221（8-[5-(2,4-二甲氧基-5-(4-三氟甲基磺酰胺基)phenyl-5-氧代戊基]-1,3,8-三氮杂螺[4.5]癸烷-2,4-二酮盐酸盐）（Ki = 2.5 μM）和SB-242084（6-氯-5-甲基-1-[6-(2-甲基吡啶-3-基氧基)吡啶-3-基甲酰基]吲哚啉）（Ki = 42.4 nM）在HUSMC PI周转分析中更有效。综上所述，这些研究强烈表明HUSMCs中存在功能活跃的5-HT2B受体亚型。该受体在这些细胞中的生理作用仍有待确定。
