Sanjana V M, Robertson C R, Jamison R L
Kidney Int. 1976 Aug;10(2):139-46. doi: 10.1038/ki.1976.87.
Recent examinations of the inner medullary collecting tubule membrane in vitro have demonstrated that its reflection coefficient to urea (sigma urea) is significantly less than unity and less than sigma NaClhe presence of antidiuretic hormone. Fluid entering the inner medullary collecting tubule has a higher urea concentration and lower NaCl concentration than does the medullary interstitium, although total osmolarity is nearly equal on either side of the membrane. The transtubular difference in solute composition, together with the difference between sigma urea and sigma NaCl, should result in a driving force for extraction of water from the tubule. This hypothesis was examined in a differential analysis of water and solute fluxes across the collecting tubule epitheliu. The results indicate that this driving force contributes significantly to water extraction from the inner medullary collecting tubule.
最近对髓质内集合管膜进行的体外研究表明，在抗利尿激素存在的情况下，其对尿素的反射系数（σ尿素）明显小于1，且小于σ氯化钠。进入髓质内集合管的液体比髓质间质具有更高的尿素浓度和更低的氯化钠浓度，尽管膜两侧的总渗透压几乎相等。溶质组成的跨管差异，以及σ尿素和σ氯化钠之间的差异，应该会产生从肾小管中提取水的驱动力。这一假设在对跨集合管上皮的水和溶质通量进行的差异分析中得到了检验。结果表明，这种驱动力对从髓质内集合管中提取水有显著贡献。
