Axial compartmentation of descending and ascending thin limbs of Henle's loops

作者：Westrick Kristen Y; Serack Bradley; Dantzler William H; Pannabecker Thomas L^*

来源：American Journal of Physiology - Renal Fluid and Electrolyte Physiology, 2013, 304(3): F308-F316.

DOI：10.1152/ajprenal.00547.2012

• aquaporin
• concentrating mechanism
• urea transport
• tubule permeability
• renal anatomy

Westrick KY, Serack B, Dantzler WH, Pannabecker TL. Axial compartmentation of descending and ascending thin limbs of Henle's loops. Am J Physiol Renal Physiol 304: F308-F316, 2013. First published November 28, 2012; doi:10.1152/ajprenal.00547.2012.-In the inner medulla, radial organization of nephrons and blood vessels around collecting duct (CD) clusters leads to two lateral interstitial regions and preferential intersegmental fluid and solute flows. As the descending (DTLs) and ascending thin limbs (ATLs) pass through these regions, their transepithelial fluid and solute flows are influenced by variable transepithelial solute gradients and structure-to-structure interactions. The goal of this study was to quantify structure-to-structure interactions, so as to better understand compartmentation and flows of transepithelial water, NaCl, and urea and generation of the axial osmotic gradient. To accomplish this, we determined lateral distances of AQP1-positive and AQP1-negative DTLs and ATLs from their nearest CDs, so as to gauge interactions with intercluster and intracluster lateral regions and interactions with interstitial nodal spaces (INSs). DTLs express reduced AQP1 and low transepithelial water permeability along their deepest segments. Deep AQP1-null segments, prebend segments, and ATLs lie equally near to CDs. Prebend segments and ATLs abut CDs and INSs throughout much of their descent and ascent, respectively; however, the distal 30% of ATLs of the longest loops lie distant from CDs as they approach the outer medullary boundary and have minimal interaction with INSs. These relationships occur regardless of loop length. Finally, we show that ascending vasa recta separate intercluster AQP1-positive DTLs from descending vasa recta, thereby minimizing dilution of gradients that drive solute secretion. We hypothesize that DTLs and ATLs enter and exit CD clusters in an orchestrated fashion that is important for generation of the corticopapillary solute gradient by minimizing NaCl and urea loss.

• 出版日期2013-2