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This Article Full Text Full Text (PDF) All Versions of this Article: 294/6/F1306    most recent 00068.2008v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Pannabecker, T. L. Articles by Dantzler, W. H. PubMed PubMed Citation Articles by Pannabecker, T. L. Articles by Dantzler, W. H.

Quantitative analysis of functional reconstructions reveals lateral and axial zonation in the renal inner medulla

Department of Physiology, University of Arizona Health Sciences Center, Tucson, Arizona

Submitted 7 February 2008 ; accepted in final form 11 April 2008

Three-dimensional functional reconstructions of descending thin limbs (DTLs) and ascending thin limbs (ATLs) of loops of Henle, descending vasa recta (DVR), ascending vasa recta (AVR), and collecting ducts (CDs) permit quantitative definition of lateral and axial zones of probable functional significance in rat inner medulla (IM). CD clusters form the organizing motif for loops of Henle and vasa recta in the initial 3.0–3.5 mm of the IM. Using Euclidean distance mapping, we defined the lateral boundary of each cluster by pixels lying maximally distant from any CD. DTLs and DVR lie almost precisely on this independently defined boundary, placing them in the intercluster interstitium maximally distant from any CD. ATLs and AVR lie in a nearly uniform pattern throughout intercluster and intracluster regions, which we further differentiated by a polygon around CDs in each cluster. Loops associated with individual CD clusters show a similar axial exponential decrease as all loops together in the IM. Because 3.0–3.5 mm below the IM base CD clusters cease to form the organizing motif, all DTLs lack aquaporin 1 (AQP1), and all vasa recta are fenestrated, we have designated the first 3.0–3.5 mm of the IM the "outer zone" (OZ) and the final 1.5–2.0 mm the "inner zone" (IZ). We further subdivided these into OZ-1, OZ-2, IZ-1, and IZ-2 on the basis of the presence of completely AQP1-null DTLs only in the first 1 mm and on broad transverse loop bends only in the final 0.5 mm. These transverse segments expand surface area for probable NaCl efflux around loop bends from 40% to 140% of CD surface area in the final 100 µm of the papilla.

countercurrent systems; concentrating mechanism; aquaporin; kidney-specific chloride channel; urea transporter B; three-dimensional reconstruction