Fatatis A, Bassi A, Iannotti E, Caso N, Mita G D, Di Renzo G, Annunziato L
Department of Neuroscience, School of Medicine, Federico II University of Naples, Italy.
J Neurochem. 1994 Nov;63(5):1900-7. doi: 10.1046/j.1471-4159.1994.63051900.x.
LAN-1 is a human neuroblastoma cell line that, in the undifferentiated state, does not respond to membrane depolarization with an elevation of [Ca2+]i, monitored by fura-2 single-cell microfluorimetry. The exposure of LAN-1 cells to the differentiating agent retinoic acid induced the appearance of [Ca2+]i elevation elicited by 55 mM K+. Maitotoxin, a putative activator of voltage-sensitive Ca2+ channels, did not evoke an elevation of [Ca2+]i in undifferentiated LAN-1 cells, but produced a marked and sustained increase in [Ca2+]i when superfused in retinoic acid-treated cells. Both high K(+)- and maitotoxin-induced [Ca2+]i elevation in retinoic acid-differentiated LAN-1 cells was reversed by the lanthanide Gd3+, an inorganic Ca(2+)-entry blocker, and by the snail toxin omega-conotoxin GVIA, which interacts with the N subtype of voltage-sensitive Ca2+ channels. In contrast, both Bay K 8644 and nimodipine, dihydropyridines that selectively activate or block, respectively, the L-channel subtype, were completely ineffective. The tumor promoter phorbol 12-myristate 13-acetate (100 nM), a protein kinase C activator, inhibited the elevation of [Ca2+]i due to Ca2+ influx elicited by membrane depolarization. K(+)-induced [Ca2+]i elevation appeared 24 h after the addition of retinoic acid and reached the highest magnitude after 72 h. Furthermore, 8 days after the removal of the differentiating agent from the culture medium, the high K(+)-induced increase of [Ca2+]i was still present.(ABSTRACT TRUNCATED AT 250 WORDS)
LAN-1是一种人神经母细胞瘤细胞系，在未分化状态下，通过fura-2单细胞显微荧光测定法监测，它对膜去极化不产生细胞内钙离子浓度（[Ca2+]i）升高的反应。将LAN-1细胞暴露于分化剂视黄酸中，可诱导由55 mM钾离子引发的[Ca2+]i升高现象的出现。刺尾鱼毒素是一种推测的电压敏感性钙离子通道激活剂，在未分化的LAN-1细胞中不会引起[Ca2+]i升高，但在视黄酸处理过的细胞中进行灌流时，会使[Ca2+]i产生显著且持续的增加。在视黄酸分化的LAN-1细胞中，高钾离子和刺尾鱼毒素诱导的[Ca2+]i升高，可被镧系元素钆离子（一种无机钙离子内流阻滞剂）以及与电压敏感性钙离子通道N亚型相互作用的蜗牛毒素ω-芋螺毒素GVIA逆转。相比之下，分别选择性激活或阻断L通道亚型的二氢吡啶类药物Bay K 8644和尼莫地平则完全无效。肿瘤促进剂佛波醇12-肉豆蔻酸酯13-乙酸酯（100 nM）是一种蛋白激酶C激活剂，可抑制因膜去极化引起的钙离子内流导致的[Ca2+]i升高。钾离子诱导的[Ca2+]i升高在添加视黄酸后24小时出现，并在72小时后达到最高幅度。此外，从培养基中去除分化剂8天后，高钾离子诱导的[Ca2+]i增加仍然存在。（摘要截断于250字）
