Günther T
Institute of Molecular Biology and Biochemistry, Free University of Berlin, FRG.
Miner Electrolyte Metab. 1993;19(4-5):259-65.
Net Mg2+ efflux occurred in human, chicken and rat erythrocytes, rat thymocytes and HL60 cells when the concentration of intracellular free Mg2+ ([Mg2+]i) was experimentally increased and proceeded until the original cellular Mg2+ content was reached, indicating induction and regulation of net Mg2+ efflux by increased [Mg2+]i. Net Mg2+ efflux was performed by electroneutral Na+/Mg2+ antiport, driven by the extra-/intracellular Na+ gradient. Na+/Mg2+ antiport was irreversible, performing only net Mg2+ efflux. Na+/Mg2+ antiport was inhibited by amiloride, quinidine and imipramine. Besides increased [Mg2+]i, Na+/Mg2+ antiport in thymocytes was regulated by cAMP which induced a maximal rate of Na+/Mg2+ antiport. Net Mg2+ influx occurred when the cellular Mg2+ content was experimentally reduced and stopped when after reincubation in suitable media the original cellular Mg2+ content was reached, indicating regulation by [Mg2+]i via feedback inhibition. Net Mg2+ influx in isolated hepatocytes was dependent on extracellular Mg2+, Na+, Cl-, HCO3- and Pi. Net Mg2+ influx may operate via electroneutral Na+, Mg2+/anion cotransport, driven by the extra-/intracellular Na+ gradient. However, electrogenic Mg2+ influx gated by extracellular Na+ and anions cannot be excluded. Net Mg2+ influx was stimulated by cAMP and inhibited by amiloride and verapamil. Net Mg2+ efflux and net Mg2+ influx are separate and regulated pathways, establishing homeostasis of intracellular Mg2+.
当通过实验提高人、鸡和大鼠红细胞、大鼠胸腺细胞及HL60细胞内游离镁离子浓度（[Mg2+]i）时，会发生净镁离子外流，该过程持续进行直至达到原始细胞镁含量，这表明[Mg2+]i升高可诱导和调节净镁离子外流。净镁离子外流通过电中性的Na+/Mg2+逆向转运体进行，由细胞外/内的钠离子梯度驱动。Na+/Mg2+逆向转运体是不可逆的，仅进行净镁离子外流。Na+/Mg2+逆向转运体受到阿米洛利、奎尼丁和丙咪嗪的抑制。除了[Mg2+]i升高外，胸腺细胞中的Na+/Mg2+逆向转运体还受cAMP调节，cAMP可诱导Na+/Mg2+逆向转运体的最大速率。当通过实验降低细胞镁含量时会发生净镁离子内流，在合适培养基中再孵育至达到原始细胞镁含量时净镁离子内流停止，这表明[Mg2+]i通过反馈抑制进行调节。分离的肝细胞中的净镁离子内流依赖于细胞外镁离子、钠离子、氯离子、碳酸氢根离子和磷酸根离子。净镁离子内流可能通过电中性的Na+、Mg2+/阴离子共转运体进行，由细胞外/内的钠离子梯度驱动。然而，不能排除由细胞外钠离子和阴离子门控的电生性镁离子内流。净镁离子内流受到cAMP刺激，受到阿米洛利和维拉帕米抑制。净镁离子外流和净镁离子内流是独立且受调节的途径,共同维持细胞内镁的稳态。
