Document Detail

Characterisation of three pathways for osmolyte efflux in human erythroleukemia cells.
MedLine Citation:
PMID:  17698149     Owner:  NLM     Status:  MEDLINE    
Cell volume decrease is a key step during differentiation of erythroid cells. This could arise from membrane transporter activation leading to a loss of cell osmolytes; however, the pathways involved are poorly understood. We have characterised Cl(-)-independent K(+) and (3)H-taurine efflux from the erythroleukemia cell line, K562. K(+) efflux (measured using (86)Rb(+)) from pre-loaded cells subjected to hypo-osmotic challenge demonstrated two phases, a rapid increase in K(+) efflux followed by a smaller slower increase. Swelling-activated taurine efflux only demonstrated a single phase. Both phases of K(+) efflux were significantly (P<0.05) blocked by anion channel inhibitor 5-nitro-2-(3-phenypropylamino)-benzoic acid (NPPB). However the antiestrogen, tamoxifen, only inhibited the slow late phase. The initial rapid phase had a higher IC(50) for NPPB inhibition than the slow phase, and was insensitive to protein kinases inhibitors KN-62, wortmannin and PD98059. For the slow K(+) efflux phase, the IC(50) for NPPB inhibition and the inhibition by KN-62, wortmannin, genistein or PD98059, were very similar to those measured for the hypo-osmotically-activated taurine efflux. With NPPB (100 microM) present, the slow K(+) efflux phase was further significantly decreased by the Ca(2+) chelator BAPTA-AM or by the Ca(2+)-activated K(+) channel blockers clotrimazole and charybdotoxin but not by apamin. Thus, at least 3 Cl(-)-independent pathways are involved: (a) a tamoxifen-sensitive and taurine-permeable anion channel; (b) a tamoxifen-insensitive and taurine-impermeable K(+) efflux pathway; and (c) a subtype of Ca(2+)-activated K(+) channel. Any or all of these could be involved in the cell volume decrease associated with differentiation in K562 cells.
Chiun-Chien Huang; Andrew C Hall; Poh-Hong Lim
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't     Date:  2007-07-18
Journal Detail:
Title:  Life sciences     Volume:  81     ISSN:  0024-3205     ISO Abbreviation:  Life Sci.     Publication Date:  2007 Aug 
Date Detail:
Created Date:  2007-08-27     Completed Date:  2007-10-12     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  0375521     Medline TA:  Life Sci     Country:  England    
Other Details:
Languages:  eng     Pagination:  732-9     Citation Subset:  IM    
Department of Physiology, Chung Shan Medical University, Taichung 40203, Taiwan, ROC.
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MeSH Terms
Biological Transport, Active
Cell Differentiation / physiology*
Cell Membrane / metabolism*
Cell Size
Chlorides / metabolism
K562 Cells
Osmolar Concentration
Potassium Channel Blockers / pharmacology
Potassium Channels / metabolism*
Rubidium Radioisotopes
Taurine / metabolism*
Reg. No./Substance:
0/Chlorides; 0/Potassium Channel Blockers; 0/Potassium Channels; 0/Rubidium Radioisotopes; 107-35-7/Taurine

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

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