Document Detail

Functional characterization of a high-affinity choline transport system in human keratinocytes.
MedLine Citation:
PMID:  12164933     Owner:  NLM     Status:  MEDLINE    
This study was performed to characterize the mechanism of choline transport into human keratinocytes. Uptake of [3H]choline was measured both in the HaCaT cell line and in native keratinocytes. Uptake in HaCaT cells was linear with time at least up to 10 min. There was little dependence of choline transport on sodium. Choline uptake was slightly stimulated by extracellular H+ with the pH optimum being 7.5. The uptake rate was saturable and indicated participation of a single transport system (Kt = 14.8 +/- 1.0 micro M, Vmax = 1.0 +/- 0.01 nmol per 10 min per mg protein). The choline uptake into HaCaT cells was inhibited by unlabeled choline, hemicholinium-3, and acetylcholine. The prototypical organic cation tetraethylammonium showed very little affinity for the choline uptake system in these cells. Several cationic drugs such as diphenhydramine, clonidine, and atropine also interacted with the transport system. Choline uptake in normal keratinocytes was very similar to that in HaCaT cells with respect to substrate specificity and affinity. We conclude that keratinocytes express a Na+ independent, high-affinity choline transport system. This system accepts many pharmacologically important organic cations as substrates. It is similar or identical to the choline carrier described in intestinal epithelial cells and in endothelial cells of the blood-brain barrier. The choline carrier seems to have relevance not only for the uptake of cationic drugs into the keratinocytes but also for the biosynthesis of skin lipids.
Kathrin Hoffmann; Franziska Grafe; Wolfgang Wohlrab; Reinhard H Neubert; Matthias Brandsch
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  The Journal of investigative dermatology     Volume:  119     ISSN:  0022-202X     ISO Abbreviation:  J. Invest. Dermatol.     Publication Date:  2002 Jul 
Date Detail:
Created Date:  2002-08-07     Completed Date:  2002-09-17     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  0426720     Medline TA:  J Invest Dermatol     Country:  United States    
Other Details:
Languages:  eng     Pagination:  118-21     Citation Subset:  IM    
Department of Pharmacy, Institute of Pharmaceutics and Biopharmaceutics, Biozentrum of the University, Martin-Luther-University Halle-Wittenberg, D-06120 Halle/Saale, Germany.
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MeSH Terms
Biological Transport / physiology
Carrier Proteins / metabolism
Cells, Cultured
Choline / pharmacokinetics*
Drug Delivery Systems
Hydrogen-Ion Concentration
Keratinocytes / cytology,  metabolism*
Skin / cytology,  metabolism*
Sodium / metabolism
Tritium / diagnostic use
Reg. No./Substance:
0/Carrier Proteins; 10028-17-8/Tritium; 62-49-7/Choline; 7440-23-5/Sodium

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

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