Document Detail

Ion transport in a human lens epithelial cell line exposed to hyposmotic and apoptotic stress.
MedLine Citation:
PMID:  20049853     Owner:  NLM     Status:  MEDLINE    
Membrane transport changes in human lens epithelial (HLE-B3) cells under hyposmotic and apoptotic stress were compared. Cell potassium content, K(i), uptake of the K congener rubidium, Rb(i), and water content were measured after hyposmotic stress induced by hypotonicity, and apoptotic stress by the protein-kinase inhibitor staurosporine (STP). Cell water increased in hyposmotic (150 mOsm) as compared to isosmotic (300 mOsm) balanced salt solution (BSS) by >2-fold at 5 min and decreased within 15 min to baseline values accompanied by a 40% K(i) loss commensurate with cell swelling and subsequent cell shrinkage likely due to regulatory volume decrease (RVD). Loss of K(i), and accompanying water, and Rb(i) uptake in hyposmotic BSS were prevented by clotrimazole (CTZ) suggesting water shifts associated with K and Rb flux via intermediate conductance K (IK) channels, also detected at the mRNA and protein level. In contrast, 2 h after 2 microM STP exposure, the cells lost approximately 40% water and approximately 60% K(i), respectively, consistent with apoptotic volume decrease (AVD). Indeed, water and K(i) loss was at least fivefold greater after hyposmotic than after apoptotic stress. High extracellular K and 2 mM 4-aminopyridine (4-AP) but not CTZ significantly reduced apoptosis. Annexin labeling phosphatidylserine (PS) at 15 min suggested loss of lipid asymmetry. Quantitative PCR revealed significant IK channel expression during prolonged hyposmotic stress. Results suggest in HLE-B3 cells, IK channels likely partook in and were down regulated after RVD, whereas pro-apoptotic STP-activation of 4-AP-sensitive voltage-gated K channels preceded or accompanied PS externalization before subsequent apoptosis.
Ameet A Chimote; Norma C Adragna; Peter K Lauf
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Publication Detail:
Type:  Comparative Study; Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Journal of cellular physiology     Volume:  223     ISSN:  1097-4652     ISO Abbreviation:  J. Cell. Physiol.     Publication Date:  2010 Apr 
Date Detail:
Created Date:  2010-02-01     Completed Date:  2010-03-08     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  0050222     Medline TA:  J Cell Physiol     Country:  United States    
Other Details:
Languages:  eng     Pagination:  110-22     Citation Subset:  IM    
Copyright Information:
J. Cell. Physiol. 223: 110-122, 2010. (c) 2009 Wiley-Liss, Inc.
Cell Biophysics Group, Boonshoft School of Medicine, Wright State University, Dayton, Ohio 45435, USA.
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MeSH Terms
4-Aminopyridine / pharmacology
Annexin A5 / metabolism
Apoptosis* / drug effects
Blotting, Western
Cell Line
Cell Size
Epithelial Cells / drug effects,  metabolism*,  pathology
Hypotonic Solutions
Intermediate-Conductance Calcium-Activated Potassium Channels / drug effects,  genetics,  metabolism*
Ion Transport
Lens, Crystalline / drug effects,  metabolism*,  pathology
Osmotic Pressure
Potassium / metabolism*
Potassium Channel Blockers / pharmacology
Protein Kinase Inhibitors / pharmacology
RNA, Messenger / metabolism
Reverse Transcriptase Polymerase Chain Reaction
Rubidium / metabolism
Signal Transduction
Staurosporine / pharmacology
Stress, Physiological*
Time Factors
Water / metabolism
Reg. No./Substance:
0/Annexin A5; 0/Hypotonic Solutions; 0/Intermediate-Conductance Calcium-Activated Potassium Channels; 0/Potassium Channel Blockers; 0/Protein Kinase Inhibitors; 0/RNA, Messenger; 504-24-5/4-Aminopyridine; 62996-74-1/Staurosporine; 7440-09-7/Potassium; 7440-17-7/Rubidium; 7732-18-5/Water

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

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