Theories which attempt to explain urinary concentrating ability generally neglect the role of medullary microcirculation. The anatomical heterogeneity of the outer medulla and inner medulla as well as the marked difference between descending and ascending vasa recta ultrastructure provide evidence that these capillaries are highly evolved to participate in this process. Our overall objective is to measure transport characteristics of the vasa recta and employ that information to predict countercurrent exchanger efficiency of small solutes, macromolecules and water.
The specific aims of this project are the following. 1) To determine the effect of albumin concentration on hydraulic conduc- tivity. The change in transcapillary volume flux will be measured as albumin concentration of the bath and perfusate is simultaneously altered. 2) To determine hydraulic conductivity. An increase in transcapillary volume flux will be induced with a high molecular weight dextran and measured. 3) To determine the reflection coefficient to albumin. The increase in transcapillary volume flux induced by albumin will be measured. 4) To determine the diffusive permeability to albumin. The lumen-to-bath flux of radiolabeled albumin will be measured. 5) To measure the transcapillary flux of neutral dextran probes. Pore theory will be applied to calculate the pore radius of the capillary wall. Finally, we will extend previous mathematical models of the micro- circulation to address both the importance of the anatomical heterogeneity of the inner and outer medullary microcirculatory beds and the transcapillary transport of albumin.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
First Independent Research Support & Transition (FIRST) Awards (R29)
Project #
5R29DK042495-02
Application #
3464127
Study Section
General Medicine B Study Section (GMB)
Project Start
1990-09-01
Project End
1995-08-31
Budget Start
1991-09-01
Budget End
1992-08-31
Support Year
2
Fiscal Year
1991
Total Cost
Indirect Cost
Name
Pennsylvania State University
Department
Type
Schools of Medicine
DUNS #
129348186
City
Hershey
State
PA
Country
United States
Zip Code
17033
Zhang, Zhong; Payne, Kristie; Pallone, Thomas L (2014) Syncytial communication in descending vasa recta includes myoendothelial coupling. Am J Physiol Renal Physiol 307:F41-52
Zhang, Zhong; Lin, Hai; Cao, Chunhua et al. (2014) Descending vasa recta endothelial cells and pericytes form mural syncytia. Am J Physiol Renal Physiol 306:F751-63
Pallone, Thomas L (2014) Complex vascular bundles, thick ascending limbs, and aquaporins: wringing out the outer medulla. Am J Physiol Renal Physiol 306:F505-6
Zhang, Zhong; Payne, Kristie; Cao, Chunhua et al. (2013) Mural propagation of descending vasa recta responses to mechanical stimulation. Am J Physiol Renal Physiol 305:F286-94
Zhang, Zhong; Lin, Hai; Cao, Chunhua et al. (2010) Voltage-gated divalent currents in descending vasa recta pericytes. Am J Physiol Renal Physiol 299:F862-71
Pallone, T L (1992) Molecular sieving of albumin by the ascending vasa recta wall. J Clin Invest 90:30-4
Pallone, T L (1991) Transport of sodium chloride and water in rat ascending vasa recta. Am J Physiol 261:F519-25