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) Other

Journal

Title: American Journal of Physiology - Renal Fluid and Electrolyte Physiology

Vol. 272

Pages: F632-F639

ISSN: 0363-6127

Publisher: American Physiological Society

Other information

Authenticus ID: P-00W-KM7

DOI: 10.1152/ajprenal.1997.272.5.f632

Abstract (EN): <jats:p> 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 5-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 microM, 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 microM. 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 microM. 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. </jats:p>

Language: English

Type (Professor's evaluation): Scientific