Competitive and non-competitive inhibition of L-3,4-dihydroxyphenylalanine uptake in Opossum kidney cells

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

Authors

Pedro Gomes (Author) Other; Maria Paula Serrão (Author) REIT; vieira-coelho, ma (Author) Other; soares-da-silva, p (Author) FMUP

Journal

Title: European Journal of Pharmacology

Vol. 332

Pages: 219-225

ISSN: 0014-2999

Publisher: Elsevier

Indexing

ISI Web of Knowledge - 4 Citations

Scopus - 4 Citations

Other information

Authenticus ID: P-001-AX6

DOI: 10.1016/s0014-2999(97)01083-2

Abstract (EN): The present study aimed to determine the kinetics of L-3,4-dihydroxyphenylalanine (L-DOPA) uptake in Opossum kidney (OK) cells and to define the type of inhibition produced by L-5-hydroxytryptophan (L-5-HTP), cyanine 863 and 3,3'-diethyloxacarbocyanine (3,3'-DOC). Non-linear analysis of the saturation curves revealed for L-DOPA a K-m (in mu M) of 129 (114, 145) and a V-max (in nmol/mg protein per 6 min) of 30.0 +/- 0.4. IC50 values for L-5-HTP (1454 mu M) obtained in the presence of a nearly saturating (250 mu M) concentration of L-DOPA were almost 4-fold those obtained when non-saturating (25 mu M) concentrations of L-DOPA were used (330). IC50 values for cyanine 863 and 3,3'-DOC (638 and 353 mu M) obtained in the presence of a nearly saturating (250 mu M) concentration of L-DOPA were similar to those obtained when non-saturating (25 mu M) concentrations of L-DOPA were used (654 and 339 mu M). V-max values (in nmol/mg protein per 6 min) for L-DOPA uptake were identical in the absence (36.4 +/- 0.7) and the presence of L-5-HTP (39.2 +/- 1.3), but K-m values (mu M) were significantly greater (P < 0.05) when L-DOPA uptake was studied in the presence of L-5-HTP (121 (100, 142) versus 318 (237, 399)). In contrast, the effect of cyanine 863 and 3,3'-DOC was to cause a significant reduction in V-max values without significant changes in K-m values. It is concluded that L-5-HTP exerts a competitive type of inhibition of L-DOPA uptake in cultured OK cells, whereas both cyanine 863, an organic cation transport inhibitor and 3,3'-DOC behave as non-competitive inhibitors. (C) 1997 Elsevier Science B.V.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 7