Lechene C, Crabos M, Bianchi G, Cantiello H
Harvard Medical School, Boston, Massachusetts.
Nephrologie. 1989;10(2):59-64.
Mammalian cells have the same hydroelectrolytic composition (high K, low Na), highly different from that of their surrounding. Constancy of cellular composition is insured by the balance between ionic leaks and (Na, K)-pump activity. Ionic leaks, specially sodium, are fundamental. They allow cells to perform a majority of their general and special functions (import of aminoacids, glucose, phosphates; export of acids; nerve influx; muscular contraction; glandular secretion; intestinal and renal reabsorption and secretion). (Na, K)-pump is essential to life. It is a kind of general motor that creates and maintains ionic concentrations differences whose potential energy is dissipated by leaks to perform cellular functions. Constancy of hydroelectrolytic intracellular composition hides that leak and pump rates, equivalent between them, are extremely variable among cell types (more than 200 times), and can increase 4 times in less than one minute within a cell type with cellular activity. In a cell, (Na, K)-pump rate is far from maximum velocity. This rate is adjusted nearly instantaneously to balance variations in leak rates; it may undergo short term modulation by endo or exocellular factors; it may undergo long term changes through synthesis of new enzyme molecules. Studies on whole cells of the balance between leaks and pump rates is necessary to understand these cells physiology and pathology. Balance between leaks and (Na, K)-pump activity is altered in renal cells from hypertensive rats, spontaneously (SHR) or genetically selected (Milan Hypertensive Strain: MHS). Strikingly, sodium activation of (Na, K)-pump of inner medullary collecting duct cells of MHS rats is greatly blunted compared to controls.
哺乳动物细胞具有相同的水电解质组成（高钾、低钠），与周围环境的组成截然不同。细胞组成的恒定通过离子泄漏与（钠，钾）-泵活性之间的平衡来保证。离子泄漏，特别是钠泄漏，至关重要。它们使细胞能够执行其大部分一般和特殊功能（氨基酸、葡萄糖、磷酸盐的摄取；酸的排出；神经内流；肌肉收缩；腺体分泌；肠道和肾脏的重吸收与分泌）。（钠，钾）-泵对生命至关重要。它是一种通用的动力装置，可产生并维持离子浓度差异，其势能通过泄漏来耗散以执行细胞功能。细胞内水电解质组成的恒定掩盖了泄漏和泵速率（二者相当）在不同细胞类型之间变化极大（超过200倍）这一事实，并且在细胞活跃时，同一细胞类型内该速率可在不到一分钟内增加4倍。在一个细胞中，（钠，钾）-泵速率远未达到最大速度。该速率几乎能瞬间调整以平衡泄漏速率的变化；它可能会受到细胞内或细胞外因素的短期调节；它可能会通过新酶分子的合成发生长期变化。研究整个细胞中泄漏和泵速率之间的平衡对于理解这些细胞的生理和病理情况很有必要。自发性高血压大鼠（SHR）或基因选择的高血压大鼠（米兰高血压品系：MHS）的肾细胞中，泄漏与（钠，钾）-泵活性之间的平衡发生了改变。令人惊讶的是，与对照组相比，MHS大鼠髓质内集合管细胞的（钠，钾）-泵对钠的激活作用大大减弱。
