AJP - Renal Add DOIs to your references at manuscript stage!
HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
QUICK SEARCH:   [advanced]


     

Am J Physiol Renal Physiol 283: F1237-F1251, 2002. First published August 6, 2002; doi:10.1152/ajprenal.00162.2002
0363-6127/02 $5.00
This Article
Right arrow Full Text
Right arrow Full Text (PDF)
Right arrow All Versions of this Article:
283/6/F1237    most recent
00162.2002v1
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Right arrow Citation Map
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in ISI Web of Science
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via ISI Web of Science (9)
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Weinstein, A. M.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Weinstein, A. M.
Vol. 283, Issue 6, F1237-F1251, December 2002

A mathematical model of rat collecting duct I. Flow effects on transport and urinary acidification

Alan M. Weinstein

Department of Physiology and Biophysics, Weill Medical College of Cornell University, New York, New York 10021

A mathematical model of the rat collecting duct (CD) has been developed by concatenating previously published models of cortical (Weinstein AM. Am J Physiol Renal Physiol 280: F1072-F1092, 2001); outer medullary (Weinstein AM. Am J Physiol Renal Physiol 279: F24-F45, 2000); and inner medullary segments (Weinstein AM. Am J Physiol Renal Physiol 274: F841-F855, 1998). Starting with end-distal tubular flow rate and composition, plus interstitial solute profiles, the model predicts urinary solute flows, including the buffer concentrations required to assess net acid excretion. In the model CD, the interstitial corticomedullary osmotic gradient provides the basis for the flow effect on the transport of several solutes. For substances that have an interstitial accumulation and that can have diffusive secretion (e.g., urea and NH<UP><SUB>4</SUB><SUP>+</SUP></UP>), enhanced luminal flow increases excretion by decreasing luminal accumulation. For substances that are reabsorbed (e.g., K+ and HCO<UP><SUB>3</SUB><SUP>−</SUP></UP>), and for which luminal accumulation can enhance reabsorption, increasing luminal flow again increases excretion by decreasing luminal solute concentration. In model calculations, flow-dependent increases in HCO<UP><SUB>3</SUB><SUP>−</SUP></UP> and NH<UP><SUB>4</SUB><SUP>+</SUP></UP> approximately balance, so net acid excretion is little changed by flow, albeit at a higher urinary pH. The model identifies delivery flow rate to the CD as a potent determinant of urinary pH, with high flows blunting maximal acidification. At even modestly high flows (9 nl · min-1 · tubule-1, with 6% of filtered Na+ entering the CD), the model cannot achieve a urinary pH <5.5 unless the delivered HCO<UP><SUB>3</SUB><SUP>−</SUP></UP> concentration is extremely low (<2 mM). Nevertheless, simulation of Na2SO4 diuresis does yield both an increase in net acid excretion and a decrease in urinary HCO<UP><SUB>3</SUB><SUP>−</SUP></UP> (i.e., a decrease in pH) despite the increase in urinary flow. This model should provide a tool for examining hypotheses regarding transport defects underlying distal renal tubular acidosis.

potassium; ammonium; renal acid excretion; distal renal tubular acidosis


This article has been cited by other articles:


Home page
 Am. J. Physiol. Renal Physiol.Home page
A. M. Weinstein
A mathematical model of distal nephron acidification: diuretic effects
Am J Physiol Renal Physiol, November 1, 2008; 295(5): F1353 - F1364.
[Abstract] [Full Text] [PDF]

Home page
 Am. J. Physiol. Renal Physiol.Home page
L. Wu, X. Gao, R. C. Brown, S. Heller, and R. G. O'Neil
Dual role of the TRPV4 channel as a sensor of flow and osmolality in renal epithelial cells
Am J Physiol Renal Physiol, November 1, 2007; 293(5): F1699 - F1713.
[Abstract] [Full Text] [PDF]

Home page
 Nephrol Dial TransplantHome page
K. Thomsen and D. G. Shirley
A hypothesis linking sodium and lithium reabsorption in the distal nephron
Nephrol. Dial. Transplant., April 1, 2006; 21(4): 869 - 880.
[Abstract] [Full Text] [PDF]

Home page
 Am. J. Physiol. Renal Physiol.Home page
A. M. Weinstein
A mathematical model of rat distal convoluted tubule. II. Potassium secretion along the connecting segment
Am J Physiol Renal Physiol, October 1, 2005; 289(4): F721 - F741.
[Abstract] [Full Text] [PDF]

Home page
 Am. J. Physiol. Renal Physiol.Home page
A. M. Weinstein
Mathematical models of renal fluid and electrolyte transport: acknowledging our uncertainty
Am J Physiol Renal Physiol, May 1, 2003; 284(5): F871 - F884.
[Abstract] [Full Text] [PDF]

Home page
 Am. J. Physiol. Renal Physiol.Home page
A. M. Weinstein
A mathematical model of rat collecting duct II. Effect of buffer delivery on urinary acidification
Am J Physiol Renal Physiol, December 1, 2002; 283(6): F1252 - F1266.
[Abstract] [Full Text] [PDF]

Home page
 Am. J. Physiol. Renal Physiol.Home page
A. M. Weinstein
A mathematical model of rat collecting duct III. Paradigms for distal acidification defects
Am J Physiol Renal Physiol, December 1, 2002; 283(6): F1267 - F1280.
[Abstract] [Full Text] [PDF]


HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
Visit Other APS Journals Online