Increases in transepithelial vectorial Na+ transport facilitates Na+-dependent L-DOPA transport in renal OK cells

• Type: Article in International Scientific Journal
• Date: 2006

Authors

Silva, E (Author) Other; Pedro Gomes (Author) Other; soares-da-silva, p (Author) FMUP

Journal

Title: Life Sciences

Vol. 79

Pages: 723-729

ISSN: 0024-3205

Publisher: Elsevier

Indexing

ISI Web of Knowledge - 6 Citations

Scopus - 7 Citations

Other information

Authenticus ID: P-004-JKE

DOI: 10.1016/j.lfs.2006.02.018

Abstract (EN): 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 alpha(1) 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 protem/6 min) of 62 and 80 in wild type and transfected cells, respectively. The uptake of a non-saturating concentration (0.25 mu M) of [C-14]-L-DOPA in OK-WT cells was not affected by Na+ removal, whereas in OK-alpha(1) cells accumulation of [C-14]-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 [C-14]-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.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 7