Shephard K L, Rahmoune H
Clore Laboratory for Life Sciences, University of Buckingham, United Kingdom.
J Appl Physiol (1985). 1994 Mar;76(3):1156-65. doi: 10.1152/jappl.1994.76.3.1156.
An isolated preparation of the guinea pig trachea was developed. The trachea was exposed serosally to Krebs-Henseleit solution and mucosally to tidal airflow, designed to mimic conditions in vivo. The preparation establishes stable layers of airway surface liquid (ASL). Typical depth, transepithelial potential differences, and sodium activity are 200 microns, -3 mV, and 125 mM, respectively (approximate sodium concn 170 mM). When exposed to air with a vapor pressure deficit (VPD), evaporation of water occurs from ASL, ASL depth decreases, and the concentration of sodium ions in ASL increases. The water content of air passing over the trachea also increases. This measurement is compared with measurements of the change in volume of ASL, based on depth changes, to yield estimates of net water transport (NWT). Measurements of changes in the sodium content of ASL allow for the calculation of net sodium transport by the trachea. Evaporation rate, changes in the volume of ASL, NWT, and net sodium transport are all influenced by VPD. The results suggest that evaporation from ASL increases its sodium concentration (and osmotic pressure) and increases osmotically driven NWT to replace water lost. Evaporation-induced increases in the sodium concentration appear to be limited by enhanced sodium uptake at high VPD.
建立了豚鼠气管的离体标本。气管浆膜面暴露于克氏-亨氏溶液，黏膜面暴露于模拟体内情况的潮式气流。该标本建立了稳定的气道表面液体（ASL）层。典型深度、跨上皮电位差和钠活性分别为200微米、-3毫伏和125毫摩尔（钠浓度约为170毫摩尔）。当暴露于具有蒸汽压亏缺（VPD）的空气中时，ASL中的水发生蒸发，ASL深度减小，ASL中钠离子浓度增加。流经气管的空气含水量也增加。将该测量结果与基于深度变化的ASL体积变化测量结果进行比较，以得出净水运输（NWT）的估计值。测量ASL中钠含量的变化可计算气管的净钠运输。蒸发速率、ASL体积变化、NWT和净钠运输均受VPD影响。结果表明，ASL的蒸发增加了其钠浓度（和渗透压），并增加了渗透驱动的NWT以补充失去的水分。在高VPD时，蒸发引起的钠浓度增加似乎受到钠摄取增强的限制。
