Kim D, Smith T W
Am J Physiol. 1986 Jan;250(1 Pt 1):C32-9. doi: 10.1152/ajpcell.1986.250.1.C32.
Increases in intracellular Na+ concentration ([Na+]i) lead to an increase in the number of Na+ pump sites in the cell membrane. To investigate further the role of [Na+]i in the regulation of Na+-K+-ATPase sites, we studied the effect of reduced [Na+]i on the number of Na+ pump sites and Na+-K+ pump activity using spontaneously beating cultured chick ventricular cells. Cells incubated in medium containing 60, 80, 100, or 140 mM Na+ for 24 or 48 h showed an extracellular [Na+]-dependent alteration in cellular Na+ content. The number of Na+ pump sites identified by [3H]ouabain binding binding declined with decreasing levels of Na+ in the medium in a time-dependent manner over 48 h, with a concomitant increase in cellular Na+ content. Verapamil (1 microM) or tetrodotoxin (1 microM) significantly reduced cellular Na+ content by 30 min of exposure and the number of Na+ pump sites by 48 h of incubation. Na+ pump activity determined from the ouabain-sensitive 42K+ uptake rate was significantly reduced in cells grown in low Na+ for 48 h, as was pump capacity, determined in Na+-loaded cells. These results support the view that [Na+]i exerts a long-term modulating effect on the number of physiologically functional Na+ pump sites.
细胞内钠离子浓度（[Na⁺]i）的升高会导致细胞膜上钠泵位点数量增加。为了进一步研究[Na⁺]i在调节钠钾ATP酶位点中的作用，我们使用自发搏动的培养鸡心室细胞，研究了降低[Na⁺]i对钠泵位点数量和钠钾泵活性的影响。在含有60、80、100或140 mM钠离子的培养基中孵育24或48小时的细胞，其细胞内钠离子含量呈现出细胞外[Na⁺]依赖性变化。通过[³H]哇巴因结合鉴定的钠泵位点数量，在48小时内随着培养基中钠离子水平的降低而呈时间依赖性下降，同时细胞内钠离子含量增加。维拉帕米（1 microM）或河豚毒素（1 microM）在暴露30分钟时显著降低细胞内钠离子含量，在孵育48小时时显著降低钠泵位点数量。根据哇巴因敏感的⁴²K⁺摄取率测定的钠泵活性，在低钠培养基中生长48小时的细胞中显著降低，在钠负荷细胞中测定的泵容量也是如此。这些结果支持这样一种观点，即[Na⁺]i对生理功能正常的钠泵位点数量发挥长期调节作用。
