Document Detail

Increases in transepithelial vectorial Na+ transport facilitates Na+-dependent L-DOPA transport in renal OK cells.
MedLine Citation:
PMID:  16600308     Owner:  NLM     Status:  MEDLINE    
The present study evaluated the hypothesis of whether increases in vectorial Na+ transport translate into facilitation of Na+-dependent L-DOPA uptake in cultured renal epithelial tubular cells. Increases in vectorial Na+ transport were obtained in opossum kidney (OK) cells engineered to overexpress Na+-K+-ATPase after transfection of wild type OK cells with the rodent Na+-K+-ATPase alpha1 subunit. The most impressive differences between wild type and transfected OK cells are that the latter overexpressed Na+-K+-ATPase accompanied by an increased activity of the transporter. Non-linear analysis of the saturation curve for l-DOPA uptake revealed a Vmax value (in nmol mg protein/6 min) of 62 and 80 in wild type and transfected cells, respectively. The uptake of a non-saturating concentration (0.25 microM) of [14C]-L-DOPA in OK-WT cells was not affected by Na+ removal, whereas in OK-alpha1 cells accumulation of [14C]-L-DOPA was clearly dependent on the presence of extracellular Na+. When Na+ was replaced by choline, the inhibitory profile of neutral l-amino acids, but not of basic and acidic amino acids, upon [14C]-L-DOPA uptake in both cell types, was significantly greater than that observed in the presence of extracellular Na+. It is concluded that enhanced ability of OK cells overexpressing Na+-K+-ATPase to translocate Na+ from the apical to the basal cell side correlates positively with their ability to accumulate L-DOPA, which is in agreement with the role of Na+ in taking up the precursor of renal dopamine.
E Silva; P Gomes; P Soares-da-Silva
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't     Date:  2006-03-06
Journal Detail:
Title:  Life sciences     Volume:  79     ISSN:  0024-3205     ISO Abbreviation:  Life Sci.     Publication Date:  2006 Jul 
Date Detail:
Created Date:  2006-07-10     Completed Date:  2006-08-16     Revised Date:  2007-11-15    
Medline Journal Info:
Nlm Unique ID:  0375521     Medline TA:  Life Sci     Country:  England    
Other Details:
Languages:  eng     Pagination:  723-9     Citation Subset:  IM    
Institute of Pharmacology and Therapeutics, Faculty of Medicine 4200-319 Porto, Portugal.
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MeSH Terms
Biological Transport
Cell Line
Cell Membrane / metabolism
Epithelial Cells / metabolism
Ion Transport
Kidney / cytology,  metabolism*
Kidney Tubules / cytology,  metabolism
Levodopa / metabolism*
Sodium / metabolism*
Sodium-Potassium-Exchanging ATPase / metabolism*
Reg. No./Substance:
0/Levodopa; 7440-23-5/Sodium; EC ATPase

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

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