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Dynamics of long loop prebend segments in the renal inner medulla
Author(s) -
Pannabecker Thomas,
Dantzler William
Publication year - 2007
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.21.6.a907
Subject(s) - vasa recta , nephron , loop of henle , anatomy , medullary cavity , reabsorption , loop (graph theory) , biophysics , chemistry , biology , kidney , mathematics , endocrinology , combinatorics
Three‐dimensional architecture of vasculature and nephron segments in rat renal inner medulla (IM) was assessed with digital reconstructions. Segments of descending vasa recta (DVR), ascending vasa recta (AVR), descending thin limbs (DTLs), ascending thin limbs (ATLs), and collecting ducts (CDs) were identified with antibodies against segment‐specific proteins associated with solute and water transport by immunofluorescence. Because prebend segments of long DTLs exhibit robust NaCl reabsorption, their architecture is important in understanding the concentrating mechanism. We made 3‐D reconstructions of all long loops of Henle around a CD cluster that originates as 31 CDs near the inner medullary base and coalesces into a single CD near the papilla tip. The total number of loops at successive 5 μm intervals along the inner medullary axis from base to tip decreases exponentially. In contrast, the number of prebend segments at these intervals alternately decreases and increases with a periodicity of ~500 μm along this axis. This repeating periodic pattern of high and low number of prebend segments overlies the exponential decrease in total number of loops and prebends and results from the combination of exponential decline in number of long loops of Henle and fixed prebend length. AQP1‐null DTLs, whose length is proportional to total DTL length, show a uniform exponential decrease in number, as do ATLs. The periodic pattern of prebend increase and decrease, in association with nodal compartments produced by the vertical symmetrical arrangement of AVR, ATLs, and CDs plus horizontal layers of interstitial cells could possibly produce stratified layers in the solute gradient along the inner medullary axis. (NIH DK16294)