| Transport of L-carnitine in human corneal and conjunctival epithelial cells. | |
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MedLine Citation:
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PMID: 21045919 Owner: NLM Status: In-Process |
Abstract/OtherAbstract:
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PURPOSE: Previously we demonstrated expression and localization of carnitine/organic cation transporters, OCTN1 and OCTN2, in human corneal and conjunctival epithelia. The present study aimed to examine the characteristics of L-carnitine transporters in cultured human limbal corneal (HCLE) and conjunctival epithelial (HCjE) cells. METHODS: Time-course, Na(+)-dependence, kinetics, energy- and pH- dependence of L-carnitine transport were investigated by monitoring L-[(3)H]carnitine uptake into HCLE and HCjE cells. To determine the specificity of action, competition and inhibition studies were performed. RESULTS: The uptake of L-carnitine into HCLE and HCjE cells was saturable and time-dependent. An Eadie-Hofstee plot showed two distinct components: a high- and a low- affinity carnitine transport system in HCLE and/or HCjE cells. L-carnitine transport was significantly inhibited by the metabolic inhibitors (sodium azide, dinitrophenol, iodoacetic acid). The L-carnitine analogs (D-carnitine, acetyl-L-carnitine and γ-butyrobetaine), tetraethylammonium (TEA), 2-amino-2-norbornane carboxylic acid (BCH), strongly inhibited uptake of L-[(3)H]carnitine. Uptake of L-[(3)H]carnitine also required the presence of Na(+) in the external medium and the uptake activity was maximal at pH 5.5. The anti-OCTN2 antibody blocked L-carnitine uptake in both HCLE and HCjE cells whereas the anti-OCTN1 antibody did not significantly block L-carnitine uptake. CONCLUSIONS: L-carnitine is transported into HCLE and HCjE cells by an active carrier mediated transport system that is time-, Na(+)-, energy- and pH- dependent. The carnitine/organic cation transporter OCTN2 appears to play a dominant role in this process. |
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Authors:
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Shunjiang Xu; Judith L Flanagan; Peter A Simmons; Joseph Vehige; Mark D Willcox; Qian Garrett |
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Publication Detail:
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Type: Journal Article; Research Support, Non-U.S. Gov't Date: 2010-09-04 |
Journal Detail:
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Title: Molecular vision Volume: 16 ISSN: 1090-0535 ISO Abbreviation: Mol. Vis. Publication Date: 2010 |
Date Detail:
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Created Date: 2010-11-03 Completed Date: - Revised Date: - |
Medline Journal Info:
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Nlm Unique ID: 9605351 Medline TA: Mol Vis Country: United States |
Other Details:
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Languages: eng Pagination: 1823-31 Citation Subset: IM |
Affiliation:
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Brien Holden Vision Institute, The University of New South Wales, Sydney, NSW, Australia. |
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From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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