Stout Charles, Charles Andrew
Loma Linda University School of Medicine, Loma Linda, California, USA.
Glia. 2003 Sep;43(3):265-73. doi: 10.1002/glia.10257.
The extracellular concentrations of Ca(2+) and Mg(2+) are well known to play important roles in the function of the central nervous system. We examined the effects of extracellular Ca(2+) and Mg(2+) on ATP release and intercellular signaling in astrocytes. The extent of propagation of intercellular Ca(2+) waves evoked by mechanical stimulation was increased by reduction of extracellular Ca(2+) (Ca(2+)) or Mg(2+) concentration (Mg(2+)) and was decreased by elevated Mg(2+). Reduction of extracellular Ca(2+) concentration (Ca(2+)) evokes intercellular Ca(2+) signaling in astrocytes; a similar effect was observed in response to change from 5 mM Mg(2+) to 0 Mg(2+). Release of low-molecular-weight dyes and ATP was also activated by low Ca(2+) or Mg(2+) and inhibited by high Ca(2+) or Mg(2+). Astrocytes showed low Ca(2+)-activated whole cell currents consistent with currents through connexin hemichannels. These currents were inhibited by extracellular Mg(2+). We conclude that extracellular divalent cations modulate intercellular Ca(2+) signaling in astrocytes by modulating the release of ATP, possibly via connexin hemichannels.
众所周知，细胞外Ca(2+)和Mg(2+)的浓度在中枢神经系统功能中发挥重要作用。我们研究了细胞外Ca(2+)和Mg(2+)对星形胶质细胞中ATP释放和细胞间信号传导的影响。机械刺激诱发的细胞间Ca(2+)波的传播范围在细胞外Ca(2+)(Ca(2+))或Mg(2+)浓度(Mg(2+))降低时增加，在Mg(2+)升高时降低。细胞外Ca(2+)浓度(Ca(2+))降低会诱发星形胶质细胞中的细胞间Ca(2+)信号传导；从5 mM Mg(2+)变为0 Mg(2+)时也观察到类似效果。低分子量染料和ATP的释放也受到低Ca(2+)或Mg(2+)的激活，并受到高Ca(2+)或Mg(2+)的抑制。星形胶质细胞表现出与通过连接蛋白半通道的电流一致的低Ca(2+)激活的全细胞电流。这些电流受到细胞外Mg(2+)的抑制。我们得出结论，细胞外二价阳离子可能通过连接蛋白半通道调节ATP的释放，从而调节星形胶质细胞中的细胞间Ca(2+)信号传导。
