effects of dexamethasone on intracellular Ca^(2+)in its sensitive cells from neonatal mouse hippocampus

Effects of dexamethasone on intracellular Ca 2+ in its sensitive cells from neonatal mouse hippocampus and cultured cortical neurogliocytes

目的：研究地塞米松（Ｄｅｘ）对神经元和胶质细胞内钙浓度（［Ｃａ２＋］ｉ）的影响．方法：Ｆｕｒａ２ＡＭ负载小鼠海马细胞（ＮＭＨＣ）和培养的胶质细胞（ＣＣＮ）．单细胞内［Ｃａ２＋］ｉ由ＡＲＣＭＭＩＣ检测系统测定．结果：Ｄｅｘ使多数ＮＭＨＣ［Ｃａ２＋］ｉ浓度依赖地迅速升高，９６个ＮＭＨＣ中仅１０％出现［Ｃａ２＋］ｉ降低．［Ｃａ２＋］ｉ升高被无镁细胞外液阻滞、被氯化镧逆转，但不受氯化锂影响．无钙Ｈａｎｋｓ液悬浮、米非司酮（Ｍｉｆ）或河毒素均可阻断Ｄｅｘ４０－９０μｍｏｌ·Ｌ－１的升［Ｃａ２＋］ｉ效应，而Ｄｅｘ２００μｍｏｌ·Ｌ－１的效应仍被保持．４０个ＣＣＮ中５０％对Ｄｅｘ产生浓度依赖的［Ｃａ２＋］ｉ升高，并被无钙或无镁的细胞外液和Ｍｉｆ预处理抑制．结论：Ｄｅｘ快速改变海马神经元和胶质细胞内［Ｃａ２＋］ｉ．［Ｃａ２＋］ｉ的这种改变是由Ｍｇ２＋和受体相关的外钙内流及高浓度Ｄｅｘ诱发的内钙释放介导的．

AIM: To investigate the effects of dexamethasone (Dex) on intracellular free calcium ([Ca 2+ ] i) in the single neuron or neurogliocyte. ME￣TH￣ODS: Neonatal mouse hippocampal cells (NMHC) and cultured cortical neuro￣glio￣cytes (CCN) were loaded with Fura 2 AM. The [Ca 2+ ] i was measured with AR CM MIC cation measurement system. RESULTS: Most of freshly isolated NMHC exhibited a rapid and concentration dependent [Ca 2+ ] i increase after administration of Dex 40-200 μmol·L -1 . Only 10 % of NMHC showed their [Ca 2+ ] i decreases in total 96 tested cells. Dex triggered [Ca 2+ ] i rise was prevented by incubating the cells with Mg 2+ free solution and reduced by adding LaCl 3. Suspended NMHC in Ca 2+ free solution or pretreated cells with mifepristone or tetrodotoxin prevented the initial [Ca 2+ ] i increases caused by Dex 40-90 μmol·L -1 , but only diminished the later [Ca 2+ ] i rises by Dex 200 μmol·L -1 . About 50 % of tested single CCN showed a rapid and concentration related [Ca 2+ ] i increase due to Dex 90-270 μmol·L -1 exposure. This effect was partially inhibited under extracellular Ca 2+ or Mg 2+ free and mifepristone pretreat￣ment conditions. CONCLUSION: Dex pro￣duces the rapid [Ca 2+ ] i changes in both neurons and glia cells. Reactions among most cells include a Mg 2+ dependent and glucocorticoid receptor related extracellular Ca 2+ influx and a high concentration of Dex mediated intracellular Ca 2+ release.