Nguyen Minhtri K, Kurtz Ira
Division of Nephrology, David Geffen School of Medicine at UCLA, Factor Bldg., Rm. 7-155, 10833 Le Conte Ave., Los Angeles, CA 90095-1689, USA.
Am J Physiol Renal Physiol. 2004 May;286(5):F828-37. doi: 10.1152/ajprenal.00393.2003. Epub 2004 Jan 20.
Edelman et al. have empirically shown that plasma water sodium concentration (Na(+)) is equal to 1.11(Na(e) + K(e))/TBW - 25.6 (Edelman IS, Leibman J, O'Meara MP, Birkenfeld LW. J Clin Invest 37: 1236-1256, 1958). However, the physiological significance of the slope and y-intercept in this equation has not been previously considered. Our analysis demonstrates that there are several clinically relevant parameters determining the magnitude of the y-intercept that independently alter Na(+):1) osmotically inactive exchangeable Na(+) and K(+); 2) plasma water K(+) concentration; and 3) osmotically active non-Na(+) and non-K(+) osmoles. In addition, we demonstrate quantitatively the physiological significance of the slope in the Edelman equation and its role in modulating Na(+). The slope of 1.11 in this equation which Edelman et al. determined empirically can be theoretically predicted by considering the combined effect of the osmotic coefficient of Na(+) salts at physiological concentrations and Gibbs-Donnan equilibrium. In addition, our results demonstrate that the slope has an independent quantitative impact on the magnitude of the y-intercept in the Edelman equation. From a physiological standpoint, the components of both the slope and the y-intercept need to be addressed when considering the factors that modulate Na(+).
埃德尔曼等人通过实验表明，血浆水钠浓度（Na⁺）等于1.11(Na(e) + K(e))/TBW - 25.6（埃德尔曼IS、莱布曼J、奥米拉MP、伯克费尔德LW。《临床研究杂志》37: 1236 - 1256，1958年）。然而，该方程中斜率和y轴截距的生理意义此前尚未得到考虑。我们的分析表明，有几个临床相关参数决定了y轴截距的大小，这些参数会独立改变Na⁺：1）渗透惰性可交换Na⁺和K⁺；2）血浆水K⁺浓度；3）渗透活性非Na⁺和非K⁺渗透质。此外，我们定量地证明了埃德尔曼方程中斜率的生理意义及其在调节Na⁺中的作用。埃德尔曼等人通过实验确定的该方程中1.11的斜率，可以通过考虑生理浓度下Na⁺盐的渗透系数和吉布斯 - 唐南平衡的综合效应从理论上进行预测。此外，我们的结果表明，斜率对埃德尔曼方程中y轴截距的大小有独立的定量影响。从生理角度来看，在考虑调节Na⁺的因素时，需要考虑斜率和y轴截距的组成部分。
