| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
1 Division of Nephrology, University of Maryland School of Medicine, Baltimore, Maryland 21201; 2 Department of Human Anatomy and Cell Biology, University of Liverpool, Liverpool L69 3GE, United Kingdom; 3 Department of Chemical and Biological Engineering, Tufts University, Medford, Massachusetts 02155; and 4 Division of Nephrology, Stanford University School of Medicine, Stanford 94305 and Veterans Affairs, Palo Alto Health Care System, Palo Alto, California 94304
The microcirculation of the renal medulla traps NaCl and urea deposited to the interstitium by the loops of Henle and collecting ducts. Theories have predicted that countercurrent exchanger efficiency is favored by high permeability to solute. In contrast to the conceptualization of vasa recta as simple "U-tube" diffusive exchangers, many findings have revealed surprising complexity. Tubular-vascular relationships in the outer and inner medulla differ markedly. The wall structure and transport properties of descending vasa recta (DVR) and ascending vasa recta (AVR) are very different. The recent discoveries of aquaporin-1 (AQP1) water channels and the facilitated urea carrier UTB in DVR endothelia show that transcellular as well as paracellular pathways are involved in equilibration of DVR plasma with the interstitium. Efflux of water across AQP1 excludes NaCl and urea, leading to the conclusion that both water abstraction and diffusion contribute to transmural equilibration. Recent theory predicts that loss of water from DVR to the interstitium favors optimization of urinary concentration by shunting water to AVR, secondarily lowering blood flow to the inner medulla. Finally, DVR are vasoactive, arteriolar microvessels that are anatomically positioned to regulate total and regional blood flow to the outer and inner medulla. In this review, we provide historical perspective, describe the current state of knowledge, and suggest areas that are in need of further exploration.
vasa recta; microperfusion; microcirculation; water channel; urinary concentration; permeability
This article has been cited by other articles:
|
|
 |
|
  M. Sendeski, A. Patzak, T. L. Pallone, C. Cao, A. E. Persson, and P. B. Persson Iodixanol, Constriction of Medullary Descending Vasa Recta, and Risk for Contrast Medium-induced Nephropathy Radiology, June 1, 2009; 251(3): 697 - 704. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 W. C. Aird Phenotypic Heterogeneity of the Endothelium: II. Representative Vascular Beds Circ. Res., February 2, 2007; 100(2): 174 - 190. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 W. Lee-Kwon, J. H. Goo, Z. Zhang, E. P. Silldorff, and T. L. Pallone Vasa recta voltage-gated Na+ channel Nav1.3 is regulated by calmodulin Am J Physiol Renal Physiol, January 1, 2007; 292(1): F404 - F414. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 Q. Zhang, C. Cao, M. Mangano, Z. Zhang, E. P. Silldorff, W. Lee-Kwon, K. Payne, and T. L. Pallone Descending vasa recta endothelium is an electrical syncytium Am J Physiol Regulatory Integrative Comp Physiol, December 1, 2006; 291(6): R1688 - R1699. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 G.G Pinter and J.L Shohet Two fluid compartments in the renal inner medulla: a view through the keyhole of the concentrating process Phil Trans R Soc A, June 15, 2006; 364(1843): 1551 - 1561. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 D. L. Tauck Using a classic paper by Gottschalk and Mylle to teach the countercurrent model of urinary concentration Advan Physiol Educ, June 1, 2006; 30(2): 63 - 66. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
C. Cao, J. H. Goo, W. Lee-Kwon, and T. L. Pallone Vasa recta pericytes express a strong inward rectifier K+ conductance Am J Physiol Regulatory Integrative Comp Physiol, June 1, 2006; 290(6): R1601 - R1607. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J. M. Sands and D. G. Bichet Nephrogenic Diabetes Insipidus Ann Intern Med, February 7, 2006; 144(3): 186 - 194. [Full Text] [PDF]
|
|
|
|
|
|
C. Cao, W. Lee-Kwon, E. P. Silldorff, and T. L. Pallone KATP channel conductance of descending vasa recta pericytes Am J Physiol Renal Physiol, December 1, 2005; 289(6): F1235 - F1245. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 Z. Zhang, C. Cao, W. Lee-Kwon, and T. L. Pallone Descending vasa recta pericytes express voltage operated Na+ conductance in the rat J. Physiol., September 1, 2005; 567(2): 445 - 457. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 W. Lee-Kwon, J. B. Wade, Z. Zhang, T. L. Pallone, and E. J. Weinman Expression of TRPC4 channel protein that interacts with NHERF-2 in rat descending vasa recta Am J Physiol Cell Physiol, April 1, 2005; 288(4): C942 - C949. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. Mobasheri and D. Marples Expression of the AQP-1 water channel in normal human tissues: a semiquantitative study using tissue microarray technology Am J Physiol Cell Physiol, March 1, 2004; 286(3): C529 - C537. [Abstract] [Full Text]
|
|
|
|
|
|
L. Bankir, K. Chen, and B. Yang Lack of UT-B in vasa recta and red blood cells prevents urea-induced improvement of urinary concentrating ability Am J Physiol Renal Physiol, January 1, 2004; 286(1): F144 - F151. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
W. Zhang and A. Edwards Theoretical effects of UTB urea transporters in the renal medullary microcirculation Am J Physiol Renal Physiol, October 1, 2003; 285(4): F731 - F747. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J. M. Sands Urine-Concentrating Ability in the Aging Kidney Sci. Aging Knowl. Environ., June 18, 2003; 2003(24): pe15 - 15. [Abstract] [Full Text]
|
|
|
|
|
|
A. W. Cowley Jr. and R. R. Roman Countercurrent exchange in the renal medulla Am J Physiol Regulatory Integrative Comp Physiol, May 1, 2003; 284(5): R1151 - R1151. [Full Text] [PDF]
|
|
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| Visit Other APS Journals Online |
