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OPOSSUM KIDNEY CELLS TAKE UP L‐DOPA THROUGH AN ORGANIC CATION POTENTIAL‐DEPENDENT AND PROTON‐INDEPENDENT TRANSPORTER
Author(s) -
GOMES P.,
SERRÃO M.P,
VIEIRACOELHO M.A,
SOARESDASILVA P.
Publication year - 1997
Publication title -
cell biology international
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.932
H-Index - 77
eISSN - 1095-8355
pISSN - 1065-6995
DOI - 10.1006/cbir.1997.0142
Subject(s) - opossum , transporter , chemistry , proton , kidney , biophysics , pharmacology , biochemistry , biology , endocrinology , anatomy , physics , gene , quantum mechanics
The present work was aimed at studying the kinetics and nature of the l‐DOPA transporter in opossum kidney (OK) cells. Saturation experiments were performed in OK cells incubated for 6 min with increasing concentrations of l‐DOPA (10 to 2500 μm); non‐linear analysis of the saturation curve revealed for l‐DOPA a K m of 129 μm (114, 145) and a V max of 30.0±0.4 nmol mg protein −1 6 min −1 The uptake of l‐DOPA (250 μm) was inhibited in a concentration‐dependent manner by cyanine 863, an organic cation inhibitor, with a K i value of 638 (430, 947) μmthe organic anion inhibitor 4,4′‐diisothiocyanostilbene‐2,2′‐disulphonic acid (DIDS), was devoid of effect upon the uptake of l‐DOPA. The uptake of l‐DOPA (250 μm) was significantly ( P <0.02) decreased (25% reduction) when cells were incubated in the presence of 137 mm K + plus 5 mm Na + when compared with the control condition (137 mm Na + plus 5 mm K + ); substitution of NaCl by choline chloride (137 mm) did not affect l‐DOPA uptake. Similarly, inwardly or outwardly directed proton gradients of 0.5 pH units (7.9, 7.4, 6.9, 6.4 and 5.9) were found not to change l‐DOPA uptake. In conclusion, the l‐DOPA uptake system in OK cells has the characteristics of an organic cation potential‐dependent and proton‐independent transporter.