Document Detail


Does the intracellular ionic concentration or the cell water content (cell volume) determine the activity of TonEBP in NIH3T3 cells?
MedLine Citation:
PMID:  18842831     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
The transcription factor, tonicity-responsive enhancer binding protein (TonEBP), is involved in the adaptive response against hypertonicity. TonEBP regulates the expression of genes that catalyze the accumulation of osmolytes, and its transcriptional activity is increased by hypertonicity. The goal of the present investigation was to investigate whether cell shrinkage or high intracellular ionic concentration induced the activation of TonEBP. We designed a model system for isotonically shrinking cells over a prolonged period of time. Cells swelled in hypotonic medium and performed a regulatory volume decrease. Upon return to the original isotonic medium, cells shrank initially, followed by a regulatory volume increase. To maintain cell shrinkage, the RVI process was inhibited as follows: ethyl-isopropyl-amiloride inhibited the Na(+)/H(+) antiport, bumetanide inhibited the Na(+)-K(+)-2Cl(-) cotransporter, and gadolinium inhibited shrinkage-activated Na(+) channels. Cells remained shrunken for at least 4 h (isotonically shrunken cells). The activity of TonEBP was investigated with a Luciferase assay after isotonic shrinkage and after shrinkage in a high-NaCl hypertonic medium. We found that TonEBP was strongly activated after 4 and 16 h in cells in high-NaCl hypertonic medium, but not after 4 or 16 h in isotonically shrunken cells. Cells treated with high-NaCl hypertonic medium for 4 h had significantly higher intracellular concentrations of both K(+) and Na(+) than isotonically shrunken cells. This strongly suggested that an increase in intracellular ionic concentration and not cell shrinkage is involved in TonEBP activation.
Authors:
Tina Rødgaard; Kenneth Schou; Martin B Friis; Else K Hoffmann
Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't     Date:  2008-10-08
Journal Detail:
Title:  American journal of physiology. Cell physiology     Volume:  295     ISSN:  0363-6143     ISO Abbreviation:  Am. J. Physiol., Cell Physiol.     Publication Date:  2008 Dec 
Date Detail:
Created Date:  2008-12-08     Completed Date:  2009-02-20     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  100901225     Medline TA:  Am J Physiol Cell Physiol     Country:  United States    
Other Details:
Languages:  eng     Pagination:  C1528-34     Citation Subset:  IM    
Affiliation:
Department of Biology, University of Copenhagen, 13, Universitetsparken, DK-2100 Copenhagen, Denmark.
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MeSH Terms
Descriptor/Qualifier:
Animals
Cell Size
Cytoplasm / chemistry*
Gene Expression Regulation / physiology*
Hypotonic Solutions
Mice
NFATC Transcription Factors / biosynthesis*,  genetics
NIH 3T3 Cells
Osmotic Pressure / physiology
Transcription, Genetic
Water-Electrolyte Balance / physiology*
Chemical
Reg. No./Substance:
0/Hypotonic Solutions; 0/NFATC Transcription Factors

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine


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