Quastel M R, Segel G B, Lichtman M A
J Cell Physiol. 1981 May;107(2):165-70. doi: 10.1002/jcp.1041070202.
We have quantified the effect of EGTA on K exodus and uptake in human blood lymphocytes. When lymphocytes were exposed to a medium containing an EGTA concentration that resulted in an ionized Calcium (Ca) of less than 10 microM, K exodus began to increase. This increase reached nearly threefold that of the control rate in a medium containing sufficient EGTA to reduce the ionized Ca concentration below 0.1 microM. When K exodus was increased, K uptake increased proportionately. This increase in K uptake represented active transport and was associated with an 80% increase in intracellular Na concentration from 15 to 27 mM. The addition of Ca to a medium containing EGTA reversed to normal the increased K exodus and uptake. Histidine, a potent chelator of divalent cations other than Ca, had no effect on K transport. These data indicate that extracellular Ca chelation leads to an increase in lymphocyte membrane permeability and cation leak. This increased leak is associated with an elevation of the cell Na and an increase in transport to a rate equivalent to that of the exodus rate. The compensatory increase in active transport maintains the cell monovalent cation concentration within 10 to 15 mM of unperturbed levels.
我们已对乙二醇双四乙酸（EGTA）对人血淋巴细胞中钾离子外流和摄取的影响进行了定量分析。当淋巴细胞暴露于含有导致游离钙（Ca）浓度低于10微摩尔的EGTA浓度的培养基中时，钾离子外流开始增加。在含有足够EGTA以将游离钙浓度降低至0.1微摩尔以下的培养基中，这种增加达到对照速率的近三倍。当钾离子外流增加时，钾离子摄取也相应增加。这种钾离子摄取的增加代表主动转运，并与细胞内钠离子浓度从15毫摩尔增加到27毫摩尔（增加80%）相关。向含有EGTA的培养基中添加钙可使增加的钾离子外流和摄取恢复正常。组氨酸是一种除钙之外的二价阳离子的有效螯合剂，对钾离子转运没有影响。这些数据表明，细胞外钙螯合导致淋巴细胞膜通透性增加和阳离子泄漏。这种增加的泄漏与细胞内钠离子升高以及转运增加至与外流速率相当的速率相关。主动转运的代偿性增加使细胞单价阳离子浓度维持在未受干扰水平的10至15毫摩尔范围内。
