Osborne N N, Fitzgibbon F, Nash M, Liu N P, Leslie R, Cholewinski A
Nuffield Laboratory of Ophthalmology, University of Oxford, England.
Vision Res. 1993 Nov;33(16):2171-9. doi: 10.1016/0042-6989(93)90097-g.
Cultured rat retinal pigment epithelium cells are shown to contain serotonergic, 5-HT2, receptors associated with phosphoinositide turnover and mobilization of intracellular calcium. Serotonin at a concentration of 10 microM induced a 2.5-fold increase in [3H]-inositol phosphates (more than 75% is in the form of [3H]-inositol-1-phosphate) accumulation within 30 min in cells preincubated in [3H]-myo-inositol and exposed to 5 mM lithium chloride. The EC50 value of serotonin was approx. 0.9 microM and the saturation concentration was 100 microM. Serotonin analogues like tryptamine, 5-methoxytryptamine, alpha-methyl-serotonin and the 5-HT2 agonists quipazine and DOI (1-[2,5-dimethoxy-4-iodophenyl]-2-aminopropane) all stimulated InsPs accumulation to some degree. Carbachol, noradrenaline, isoproterenol, dopamine, tryptophan, 5-hydroxytryptophan, 8-hydroxy-2(di-n-propyl-amino) tetralin, 2-methyl-serotonin and NECA (5'-[N-ethyl]-carboxamidoadenosine) were inactive. The serotonin-induced response was blocked most effectively by ketanserin and methysergide but not by 5-HT3 or 5-HT1 antagonists. The serotonin response was attenuated by the active phorbol ester, 4 beta-phorbol 12-myristate 13-acetate and this was attenuated by the non-selective protein kinase C inhibitor, staurosporine. Pertussis toxin failed to influence the serotonin-mediated phosphoinositide turnover. Addition of serotonin to cultures loaded with Fura-2 showed a transient increase in calcium concentrations in most of the cells. This change in calcium was independent of external calcium and the serotonin response was attenuated by ketanserin but not by the 5-HT3 antagonist granisetron.(ABSTRACT TRUNCATED AT 250 WORDS)
培养的大鼠视网膜色素上皮细胞显示含有与磷酸肌醇代谢和细胞内钙动员相关的5-羟色胺能5-HT2受体。在[3H]-肌醇中预孵育并暴露于5 mM氯化锂的细胞中，浓度为10 microM的5-羟色胺在30分钟内使[3H]-肌醇磷酸（超过75%为[3H]-肌醇-1-磷酸形式）积累增加2.5倍。5-羟色胺的EC50值约为0.9 microM，饱和浓度为100 microM。色胺、5-甲氧基色胺、α-甲基-5-羟色胺等5-羟色胺类似物以及5-HT2激动剂喹哌嗪和DOI（1-[2,5-二甲氧基-4-碘苯基]-2-氨基丙烷）均在一定程度上刺激肌醇磷酸积累。卡巴胆碱、去甲肾上腺素、异丙肾上腺素、多巴胺、色氨酸、5-羟色氨酸、8-羟基-2（二正丙基氨基）四氢萘、2-甲基-5-羟色胺和NECA（5'-[N-乙基]-羧酰胺腺苷）无活性。5-羟色胺诱导的反应被酮色林和麦角酰二乙胺最有效地阻断，但不被5-HT3或5-HT1拮抗剂阻断。5-羟色胺反应被活性佛波酯4β-佛波醇12-肉豆蔻酸酯13-乙酸酯减弱，而这又被非选择性蛋白激酶C抑制剂星形孢菌素减弱。百日咳毒素未能影响5-羟色胺介导的磷酸肌醇代谢。向加载有Fura-2的培养物中添加5-羟色胺显示大多数细胞中的钙浓度短暂升高。这种钙变化与细胞外钙无关，5-羟色胺反应被酮色林减弱，但不被5-HT3拮抗剂格拉司琼减弱。（摘要截短于250字）
