Escobales N, Canessa M
J Biol Chem. 1985 Oct 5;260(22):11914-23.
The effect of Ca2+ on the ouabain- and bumetanide-resistant Na+ fluxes in intact red cells was studied at relatively constant internal Ca2+, membrane potential, and cell volume. The red cell calcium concentration was modified using the ionophore A23187. In fresh red cells, the Na+ influx and efflux (1.2 +/- 0.13 and 0.26 +/- 0.07 mmol/liter cells x h, respectively) were not affected by amiloride (1 mM). When external Ca2+ was raised from 0 to 150 microM, in the presence of A23187, both the Na+ influx and efflux were stimulated (about 3.5-fold). The Ca2+-activated Na+ efflux and influx had an apparent Km for activation by Ca2+o of about 25 microM. The Ca2+-dependent Na+ transport was inhibited 30-60% by amiloride (ID50 = 17.3 +/- 8 microM). Amiloride, however, had no effect on the Ca2+-dependent K+ influx. The amiloride-sensitive (AS) transport pathway was a linear function of the Na+o concentration in the range from 0 to 75 mM. The Ca2+i activation seems to depend on the metabolic integrity of red cells. 1) It does not take place in ATP-depleted red cells; 2) ATP-repletion of ATP-depleted red cells fully restored AS Na influx; and 3) ATP-enrichment (ATP-red cells) enhanced the AS Na influx by about 100%. The Ca2+-activated AS Na+ influx was not affected by either DIDS or trifluoperazine. The present results indicate that in human erythrocytes an increase in internal Ca2+ activates on otherwise silent AS Na+-transport system, which is dependent on the metabolic integrity of the red cells.
在相对恒定的细胞内钙离子浓度、膜电位和细胞体积条件下，研究了钙离子对完整红细胞中哇巴因和布美他尼耐药性钠离子通量的影响。使用离子载体A23187改变红细胞钙浓度。在新鲜红细胞中，钠离子流入和流出（分别为1.2±0.13和0.26±0.07 mmol/升细胞×小时）不受氨氯地平（1 mM）影响。当在A23187存在下将细胞外钙离子从0提高到150 μM时，钠离子流入和流出均受到刺激（约3.5倍）。钙离子激活的钠离子流出和流入对细胞外钙离子激活的表观Km约为25 μM。氨氯地平（ID50 = 17.3±8 μM）可使钙离子依赖性钠离子转运受到30 - 60%的抑制。然而，氨氯地平对钙离子依赖性钾离子流入没有影响。氨氯地平敏感（AS）转运途径是细胞外钠离子浓度在0至75 mM范围内的线性函数。钙离子内激活似乎取决于红细胞的代谢完整性。1）在ATP耗尽的红细胞中不发生；2）ATP耗尽的红细胞补充ATP可完全恢复AS钠离子流入；3）ATP富集（ATP - 红细胞）使AS钠离子流入增加约100%。钙离子激活的AS钠离子流入不受DIDS或三氟拉嗪影响。目前的结果表明，在人类红细胞中，细胞内钙离子增加可激活原本沉默的AS钠离子转运系统，该系统依赖于红细胞的代谢完整性。
