The ability to concentrate urine, and to vary urine osmolality, is critical for maintaining fluid balance. A urea transporter is critically important to the theories proposed to explain the physiologic processes occurring when urine is concentrated. Only 12 years ago, evidence for such a transporter was largely speculative, but investigations in this laboratory provided experimental evidence for facilitated urea transport in kidney. Subsequently, 2 cDNA isoforms for facilitated urea transporters were cloned from kidney medulla (UT-Al, UT-A2) and one from erythrocytes (UT-B). During the previous grant period, the applicants cloned 2 additional kidney cDNA isoforms (UT-A3, UT-A4) and the UT-A gene. Vasopressin stimulates urea permeability in perfused terminal inner medullary collecting ducts (IMCDs) within 5 minutes, and the application provides preliminary data showing that vasopressin increases the phosphorylation of UT-A 1 in rat IMCDs within 2-5 minutes. There has been progress, through those studies, in understanding the long-term regulation of urea transport. In other experiments, five animal models associated with impaired urine concentrating ability were studied. The surprising finding was that facilitated urea transport and UT-A l protein abundance are increased during in vivo conditions associated with an impaired urine concentrating ability and a reduced plasma vasopressin level. The current application proposes to: 1) identify the mechanism that regulates urea transport rapidly to test the hypothesis that rapid regulation occurs by changes in phosphorylation of specific UT-A proteins; and 2) evaluate the mechanism of long-term regulation of urea transport in a rat model of the syndrome of inappropriate antidiuretic hormone secretion (SIADH) to test the hypothesis that down-regulation of UT-A proteins is involved in the mechanisms responsible for vasopressin-escape.
Specific Aim 1 will test whether urea transporter phosphorylation is the mechanism by which vasopressin rapidly increases urea permeability in rat IMCDs.
Specific Aim 2 will identify the site(s) within UT-A proteins that are phosphorylated in response to vasopressin.
Specific Aim 3 will test whether phosphorylation is the mechanism by which other agonists (hyperosmolality, angiotensin II) rapidly stimulate urea permeability in rat IMCDs.
Specific Aim 4 will test whether UT-A expression or regulation is altered in rats with a model of SIADH or during vasopressin-escape.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
5R01DK041707-11
Application #
6380627
Study Section
Special Emphasis Panel (ZRG1-SSS-G (02))
Program Officer
Scherbenske, M James
Project Start
1989-08-01
Project End
2004-07-31
Budget Start
2001-08-01
Budget End
2002-07-31
Support Year
11
Fiscal Year
2001
Total Cost
$294,281
Indirect Cost
Name
Emory University
Department
Internal Medicine/Medicine
Type
Schools of Medicine
DUNS #
042250712
City
Atlanta
State
GA
Country
United States
Zip Code
30322
Hinze, Christian; Ruffert, Janett; Walentin, Katharina et al. (2018) GRHL2 Is Required for Collecting Duct Epithelial Barrier Function and Renal Osmoregulation. J Am Soc Nephrol 29:857-868
Kenig-Kozlovsky, Yael; Scott, Rizaldy P; Onay, Tuncer et al. (2018) Ascending Vasa Recta Are Angiopoietin/Tie2-Dependent Lymphatic-Like Vessels. J Am Soc Nephrol 29:1097-1107
Okazaki, Yuri; Nakamura, Keishi; Takeda, Shuto et al. (2018) GDE5 Inhibition Accumulates Intracellular Glycerophosphocholine and Suppresses Adipogenesis at a Mitotic Clonal Expansion Stage. Am J Physiol Cell Physiol :
Kitada, Kento; Daub, Steffen; Zhang, Yahua et al. (2017) High salt intake reprioritizes osmolyte and energy metabolism for body fluid conservation. J Clin Invest 127:1944-1959
Hou, Ruida; Alemozaffar, Mehrdad; Yang, Baoxue et al. (2017) Identification of a Novel UT-B Urea Transporter in Human Urothelial Cancer. Front Physiol 8:245
Ren, Huiwen; Yang, Baoxue; Ruiz, Joseph A et al. (2016) Phosphatase inhibition increases AQP2 accumulation in the rat IMCD apical plasma membrane. Am J Physiol Renal Physiol 311:F1189-F1197
Efe, Orhan; Klein, Janet D; LaRocque, Lauren M et al. (2016) Metformin improves urine concentration in rodents with nephrogenic diabetes insipidus. JCI Insight 1:
Klein, Janet D; Wang, Yanhua; Blount, Mitsi A et al. (2016) Metformin, an AMPK activator, stimulates the phosphorylation of aquaporin 2 and urea transporter A1 in inner medullary collecting ducts. Am J Physiol Renal Physiol 310:F1008-12
Reed, Galen D; von Morze, Cornelius; Verkman, Alan S et al. (2016) Imaging Renal Urea Handling in Rats at Millimeter Resolution using Hyperpolarized Magnetic Resonance Relaxometry. Tomography 2:125-135
Chen, Ling; LaRocque, Lauren M; Efe, Orhan et al. (2016) Effect of Dapagliflozin Treatment on Fluid and Electrolyte Balance in Diabetic Rats. Am J Med Sci 352:517-523

Showing the most recent 10 out of 108 publications