The interaction of intracellular Mg2+ and pH on Cl- fluxes associated with intracellular pH regulation in barnacle muscle fibers.
The interaction of intracellular Mg2+ and pH on Cl- fluxes associated with intracellular pH regulation in barnacle muscle fibers.
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细胞内 Mg2+ 和 pH 对 Cl-通量的相互作用与藤壶肌纤维细胞内 pH 调节相关。
DOI：
10.1085/jgp.91.4.495
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发表时间：
1988
期刊：
影响因子：
--
通讯作者：
Brodwick,MS
中科院分区：
文献类型：
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作者：
Russell,JM;Brodwick,MS
采用细胞内透析技术测定了巨型藤壶单根肌肉纤维的单向Cl-通量和净酸挤出量。当pHi低于正常水平7.35时，会刺激Cl-外排和内流。这些氯通量的增加被二磺酸二苯乙烯衍生物如sit和DIDS所阻断。sit敏感的Cl-外排严重依赖于pHi，当pHi从7.35降至6.7时，Cl-外排增加了约20倍。在正常Mg2+浓度条件下，Cl-外排激活的表观pKa为7.0。我们发现，提高[Mg2+]i，而不是[Mg2+]o，对sits敏感的单向Cl-通量和sits敏感的净酸挤压都有明显的抑制作用。增加[Mg2+]使Cl-外排的表观pKa向更酸的值移动，但不影响所能达到的最大通量。在sit敏感的Cl-外排中，pHi和[Mg2+]i之间的关系与H离子和Mg离子之间的竞争是一致的。我们得出结论，sit抑制Cl-通量是由pHi调节转运机制介导的，细胞内Mg2+水平的变化可以改变pHi调节因子/阴离子转运蛋白的活性。
The intracellular dialysis technique was used to measure unidirectional Cl- fluxes and net acid extrusion by single muscle fibers from the giant barnacle. Decreasing pHi below normal levels of 7.35 stimulated both Cl- efflux and influx. These increases of Cl- fluxes were blocked by disulfonic acid stilbene derivatives such as SITS and DIDS. The SITS-sensitive Cl- efflux was sharply dependent upon pHi, increasing approximately 20-fold as pHi was decreased from 7.35 to 6.7. Under conditions of normal intracellular Mg2+ concentration, the apparent pKa for the activation of Cl- efflux was 7.0. We found that raising [Mg2+]i, but not [Mg2+]o, had a pronounced inhibitory effect on both SITS-sensitive unidirectional Cl- fluxes as well as on SITS-sensitive net acid extrusion. Increasing [Mg2+]i shifted the apparent pKa of Cl- efflux to a more acid value without affecting the maximal flux that could be attained. This relation between pHi and [Mg2+]i on SITS-sensitive Cl- efflux is consistent with a competition between H ions and Mg ions. We conclude that the SITS-inhibitable Cl- fluxes are mediated by the pHi-regulatory transport mechanism and that changes of intracellular Mg2+ levels can modify the activity of the pHi regulator/anion transporter.