Evidence for sodium-dependent active urea secretion in the deepest subsegment of the rat inner medullary collecting duct

The Journal of Clinical Investigation
A Kato, J M Sands

Abstract

Active reabsorption of urea appears in the initial IMCD (IMCD1) of rats fed a low-protein diet. To determine whether active urea transport also occurs in the deepest IMCD subsegment, the IMCD3, we isolated IMCDs from the base (IMCD1), middle (IMCD2), and tip (IMCD3) regions of the inner medulla from rats fed a normal protein diet and water ad libitum. IMCDs were perfused with identical perfusate and bath solutions. A significant rate of net urea secretion was present only in IMCD3s. Replacing perfusate Na+ with NMDG+ reversibly inhibited net urea secretion but replacing bath Na+ with NMDG+ or perfusate Cl- with gluconate- had no effect. Net urea secretion was significantly inhibited by: (a) 250 microM phloretin (perfusate); (b) 100 nM triamterene (perfusate); (c) 1 mM ouabain (bath); and (d) cooling the tubule to 23 degrees C. Net urea secretion was significantly stimulated by 10 nM vasopressin (bath). Next, we perfused IMCD3s from water diuretic rats (given food ad libitum) and found a significant, fivefold increase in net urea secretion. In summary, we identified a secondary active, secretory urea transport process in IMCD3s of normal rats which is upregulated in water diuretic rats. This new urea transporter may be a sodium-...Continue Reading

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Citations

Feb 1, 2007·The Journal of Membrane Biology·M D McDonaldP J Walsh
Feb 1, 2007·The Journal of Membrane Biology·R A FentonM A Knepper
Sep 26, 2012·Pflügers Archiv : European journal of physiology·Janet D KleinJeff M Sands
Jun 20, 2003·Comparative Biochemistry and Physiology. Part A, Molecular & Integrative Physiology·M Danielle McDonaldPatrick J Walsh
Dec 10, 2003·Comparative Biochemistry and Physiology. Part B, Biochemistry & Molecular Biology·Chris M WoodPatrick J Walsh
Dec 10, 2003·Comparative Biochemistry and Physiology. Part B, Biochemistry & Molecular Biology·Shigehisa HiroseYoshio Takei
Jun 1, 2005·Nutrition Research Reviews·Gavin S Stewart, Craig P Smith
Sep 24, 1999·Current Opinion in Nephrology and Hypertension·J M Sands
Nov 14, 2000·Journal of Bacteriology·Y MoritaT Tsuchiya
Jan 14, 2003·Annual Review of Physiology·Jeff M Sands
Jan 8, 2010·American Journal of Physiology. Renal Physiology·Anita T LaytonHarold E Layton
Nov 18, 2011·American Journal of Physiology. Renal Physiology·Anita T LaytonThomas L Pannabecker
Apr 15, 2005·Journal of the American Society of Nephrology : JASN·Robert A FentonMark A Knepper
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Nov 4, 2006·American Journal of Physiology. Renal Physiology·Juha P Kokko, Jeff M Sands
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Dec 22, 2000·American Journal of Physiology. Regulatory, Integrative and Comparative Physiology·G A FinesP A Wright
Mar 12, 1999·Journal of the American Society of Nephrology : JASN·J M Sands

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