Titze Jens
Department of Nephrology and Hypertension and Nikolaus Fiebiger Center for Molecular Medicine, Friedrich Alexander University, Erlangen-Nurnberg, Germany.
Blood Purif. 2008;26(1):95-9. doi: 10.1159/000110573. Epub 2008 Jan 10.
Electrolyte and body fluid homeostasis in higher vertebrates is believed to be fully understood. The paradigm is that Na(+) is restricted mainly to the extracellular fluid and K(+) to the intracellular space, where both ions act to hold water and thereby control the extracellular and intracellular fluid volume by their osmotic activity. Na(+) accumulation thus inevitably leads to water retention. The constancy of the extracellular volume is the task of the kidneys, which control the total body Na(+) content. More recent data from balance studies in humans have questioned this traditional view, suggesting that large amounts of Na(+) can be accumulated without accompanying water retention by osmotically inactive Na(+) retention, or by osmotically neutral Na(+)/K(+) exchange. Besides the control of the body Na(+) content by the kidneys, redistribution of body electrolytes hence provides an extrarenal regulatory alternative in the maintenance of body fluid volume and blood pressure control.
高等脊椎动物的电解质和体液平衡被认为已得到充分理解。传统观念认为，Na⁺主要局限于细胞外液，K⁺主要存在于细胞内空间，这两种离子都起着保持水分的作用，从而通过其渗透活性控制细胞外液和细胞内液的体积。因此，Na⁺的积累不可避免地导致水潴留。细胞外液体积的恒定是肾脏的任务，肾脏控制着全身Na⁺的含量。来自人体平衡研究的最新数据对这一传统观点提出了质疑，表明大量的Na⁺可以通过无渗透活性的Na⁺潴留或渗透中性的Na⁺/K⁺交换而积累，而不会伴有水潴留。除了肾脏对体内Na⁺含量的控制外，身体电解质的重新分布因此在维持体液体积和控制血压方面提供了一种肾外调节方式。
