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Downregulation of renal TonEBP in hypokalemic rats

Title
Downregulation of renal TonEBP in hypokalemic rats
Authors
Jeon U.S.Han K.-H.Park S.-H.Lee S.D.Sheen M.R.Jung J.-Y.Kim W.Y.Sands J.M.Kim J.Kwon H.M.
Ewha Authors
한기환
SCOPUS Author ID
한기환scopus
Issue Date
2007
Journal Title
American Journal of Physiology - Renal Physiology
ISSN
0363-6127JCR Link
Citation
vol. 293, no. 1, pp. F408 - F415
Indexed
SCOPUS WOS scopus
Abstract
Hypokalemia causes a significant decrease in the tonicity of the renal medullary interstitium in association with reduced expression of sodium transporters in the distal tubule. We asked whether hypokalemia caused downregulation of the tonicity-responsive enhancer binding protein (TonEBP) transcriptional activator in the renal medulla due to the reduced tonicity. We found that the abundance of TonEBP decreased significantly in the outer and inner medullas of hypokalemic rats. Underlying mechanisms appeared different in the two regions because the abundance of TonEBP mRNA was lower in the outer medulla but unchanged in the inner medulla. Immunohistochemical examination of TonEBP revealed cell type-specific differences. TonEBP expression decreased dramatically in the outer and inner medullary collecting ducts, thick ascending limbs, and interstitial cells. In the descending and ascending thin limbs, TonEBP abundance decreased modestly. In the outer medulla, TonEBP shifted to the cytoplasm in the descending thin limbs. As expected, transcription of aldose reductase, a target of TonEBP, was decreased since the abundance of mRNA and protein was reduced. Downregulation of TonEBP appeared to have also contributed to reduced expression of aquaporin-2 and UT-A urea transporters in the renal medulla. In cultured cells, expression and activity of TonEBP were not affected by reduced potassium concentrations in the medium. These data support the view that medullary tonicity regulates expression and nuclear distribution of TonEBP in the renal medulla in cell type-specific manners. Copyright © 2007 the American Physiological Society.
DOI
10.1152/ajprenal.00502.2006
Appears in Collections:
의과대학 > 의학과 > Journal papers
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