Sethi T, Rozengurt E
Imperial Cancer Research Fund, London, United Kingdom.
Cancer Res. 1991 Mar 15;51(6):1674-9.
Addition of the neuropeptide galanin to small cell lung cancer (SCLC) cells loaded with the fluorescent Ca2+ indicator fura-2-tetraacetoxymethylester causes a rapid and transient increase in the intracellular concentration of Ca2+ ([Ca2+]i) followed by homologous desensitization. Galanin increased [Ca2+]i in a concentration-dependent fashion with half-maximum effect (EC50) at 20-22 nM in H69 and H510 SCLC cells. Galanin mobilized Ca2+ from intracellular stores since its effects on [Ca2+]i were not blocked by chelation of extracellular Ca2+. Pretreatment with pertussis toxin (200 ng/ml for 4 h) did not prevent galanin-induced Ca2+ mobilization. In contrast, direct activation of protein kinase C with phorbol esters attenuated the Ca2+ response induced by galanin. The effects of galanin could be dissociated from changes in membrane potential: galanin did not increase membrane potential in SCLC cells loaded with bis(1,3-diethyltiobarbiturate)-trimethineoxonol and induced Ca2+ mobilization in depolarized SCLC cells, i.e., in cells suspended in a solution containing 145 mM K+ instead of Na+. Galanin also caused an increase in the formation of inositol phosphates in a time- and dose-dependent manner (EC50 10 nM). A rapid increase in the inositol trisphosphate fraction was followed by a slower increase in the inositol monophosphate fraction. Galanin stimulated clonal growth of both H69 and H510 cells in semisolid (agarose-containing) medium. This growth-promoting effect was sharply dependent on galanin concentration (EC50 20 nM) and markedly inhibited by [Arg6,D-Trp7,9,MePhe8]substance P, a recently identified broad spectrum neuropeptide antagonist. The results show for the first time that galanin receptors are coupled to inositol phosphate and [Ca2+]i responses in SCLC cells and, in particular, that this neuropeptide can act as a direct growth factor for these human cancer cells.
向加载了荧光Ca2+指示剂fura-2-四乙酰氧基甲酯的小细胞肺癌（SCLC）细胞中添加神经肽甘丙肽，会导致细胞内Ca2+浓度（[Ca2+]i）迅速短暂升高，随后出现同源脱敏。甘丙肽在H69和H510 SCLC细胞中以浓度依赖方式增加[Ca2+]i，半数最大效应（EC50）在20 - 22 nM。甘丙肽从细胞内储存库中动员Ca2+，因为其对[Ca2+]i的作用不会因细胞外Ca2+螯合而被阻断。用百日咳毒素（200 ng/ml，处理4小时）预处理并不能阻止甘丙肽诱导的Ca2+动员。相反，佛波酯直接激活蛋白激酶C会减弱甘丙肽诱导的Ca2+反应。甘丙肽的作用可与膜电位变化分离：甘丙肽不会增加加载了双（1,3 - 二乙基硫代巴比妥酸）-三甲川氧羰花青的SCLC细胞的膜电位，并且在去极化的SCLC细胞中诱导Ca2+动员，即在悬浮于含145 mM K+而非Na+溶液中的细胞中。甘丙肽还以时间和剂量依赖方式（EC50 10 nM）导致肌醇磷酸形成增加。肌醇三磷酸部分迅速增加，随后肌醇单磷酸部分缓慢增加。甘丙肽刺激H69和H510细胞在半固体（含琼脂糖）培养基中的克隆生长。这种促生长作用强烈依赖于甘丙肽浓度（EC50 20 nM），并被[Arg6,D-Trp7,9,MePhe8]P物质（一种最近鉴定的广谱神经肽拮抗剂）显著抑制。结果首次表明，甘丙肽受体与SCLC细胞中的肌醇磷酸和[Ca2+]i反应偶联，特别是这种神经肽可作为这些人类癌细胞的直接生长因子。
