Apical and basal uptake of L-dopa and L-5-HTP and their corresponding amines, dopamine and 5-HT, in OK cells

• Type: Article in International Scientific Journal
• Date: 1997

Authors

vieira-coelho, ma (Author) Other; soares-da-silva, p (Author) FMUP

Journal

Title: American Journal of Physiology - Renal Physiology

Vol. 272

Pages: F632-F639

ISSN: 1931-857X

Publisher: American Physiological Society

Indexing

ISI Web of Knowledge - 21 Citations

Scopus - 22 Citations

Other information

Authenticus ID: P-001-BF7

Abstract (EN): The present study defined the kinetic characteristics of L-3,4-dihydroxyphenylalanine (L-dopa) and L-5-hydroxytryptophan (L-5-HTP) transport and their decarboxylation products, dopamine and 6-hydroxytryptamine (5-HT), respectively, in OK cells. The apical uptake of both L-dopa and 5-HTP was temperature dependent and stereoselective. Nonlinear analysis of the saturation curves revealed for L-dopa and L-5-HTP Michaelis constants of 13.8 and 29.1 mu M, respectively, and maximal velocities of 21 and 29 nmol . mg protein(-1) . 6 min(-1), respectively. L-5-HTP inhibited the apical uptake of L-dopa with a half-maximal inhibitory constant of 29.1 mu M. The accumulation of L-dopa and L-5-HTP from the basolateral cell border was dependent on the concentration used and saturable at nearly 50 mu M. The accumulation of dopamine and 5-HT was found to be saturable only when the substrates were applied from the basolateral cell border. These results demonstrate that the L-dopa and L-5-HTP transporters in OK cells are located in both the apical and basolateral cell borders, whereas the uptake of dopamine and 5-HT is a saturable process only when the substrates are applied from the basolateral cell border.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 8