Interstitial water and solute recovery by inner medullary vasa recta

被引:21
|
作者
Edwards, A
DeLong, MJ
Pallone, TL
机构
[1] Tufts Univ, Dept Chem Engn, Medford, MA 02155 USA
[2] Penn State Univ, Dept Chem Engn, University Pk, PA 16802 USA
[3] Univ Maryland, Sch Med, Div Nephrol, Baltimore, MD 21201 USA
关键词
kidney; microcirculation; vascular transport; sodium; urea; mathematical model; urinary concentration;
D O I
10.1152/ajprenal.2000.278.2.F257
中图分类号
Q4 [生理学];
学科分类号
071003 ;
摘要
A recent model of volume and solute microvascular exchange in the renal medulla was extended by simulating the deposition of NaCl, urea, and water into the medullary interstitium from the loops of Henle and collecting ducts with generation rates that undergo spatial variation within the inner medullary interstitium. To build an exponential osmolality gradient in the inner medulla, as suggested by Koepsell et al. (H. Koepsell, W. E. A. P. Nicholson, W. Kriz, and H. J. Hohling. Pflugers Arch. 350: 167-184, 1974), the ratio of the interstitial area-weighted generation rate of small solutes to that of water must increase along the corticomedullary axis. We satisfied this condition either by holding the area-weighted generation rate of water constant while increasing that of NaCl and urea or by reducing the input rate of water with medullary depth. The latter case, in particular, yielded higher solute concentrations at the papillary tip. Assuming that the fraction of the filtered load recovered by inner medullary vasa recta for water, NaCl, and urea is 1%, 1%, and 40%, respectively, papillary tip osmolality is 1,470 mosmol/kgH(2)O when urea generation and NaCl generation per unit volume of interstitium increase exponentially and linearly, respectively. The inner medullary osmolar gradient also increases further when 1) medullary blood flow is reduced, 2) hydraulic conductivity of descending vasa recta (DVR) is lowered, and 3) vasa recta permeability to NaCl and urea is maximized. The coupling between water and small solute transport, resulting from aquaporin-1-mediated transcellular flux in DVR, also enhances tip osmolality.
引用
收藏
页码:F257 / F269
页数:13
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