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The mitochondrial fluorescent dye rhodamine 123 is a high‐affinity substrate for organic cation transporters ( OCT s) 1 and 2
Author(s) -
Jouan Elodie,
Vee Marc,
Denizot Claire,
Da Violante Georges,
Fardel Olivier
Publication year - 2014
Publication title -
fundamental and clinical pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.655
H-Index - 73
eISSN - 1472-8206
pISSN - 0767-3981
DOI - 10.1111/j.1472-8206.2012.01071.x
Subject(s) - rhodamine 123 , hek 293 cells , organic cation transport proteins , rhodamine , chemistry , fluorescence , substrate (aquarium) , tetraethylammonium , biophysics , transporter , biochemistry , receptor , potassium , biology , organic chemistry , ecology , physics , quantum mechanics , multiple drug resistance , gene , antibiotics
Rhodamine 123 is a fluorescent cationic dye commonly used as a mitochondrial probe and known or suspected to be transported by certain drug membrane transporters. The present study was designed to characterize the putative interactions of rhodamine 123 with human organic cation transporter ( OCT ) 1 and OCT 2. Intracellular uptake of the dye was demonstrated to be enhanced in both h OCT 1‐ and h OCT 2‐overexpressing HEK 293 cells when compared with control HEK 293 cells. This increase of rhodamine 123 influxes was found to be a saturable carrier‐mediated process, with low K m values ( K m = 0.54 μ m and K m = 0.61 μ m for transport of the dye in h OCT 1‐ and h OCT 2‐positive HEK 293 cells, respectively). Known inhibitors of h OCT 1 and h OCT 2 activities such as verapamil, amitriptyline, prazosin, and quinine were next demonstrated to decrease rhodamine 123 accumulation in h OCT 1‐ and h OCT 2‐overexpressing HEK 293 cells. In addition, the dye was found to inhibit h OCT 1‐ and h OCT 2‐mediated uptake of tetraethylammonium ( TEA ), a model substrate for both h OCT 1 and h OCT 2; rhodamine 123 appeared nevertheless to be a more potent inhibitor of h OCT 1‐mediated TEA transport (IC 50 = 0.37 μ m ) than of that mediated by h OCT 2 (IC 50 = 61.5 μ m ). Taken together, these data demonstrate that rhodamine 123 is a high‐affinity substrate for both h OCT 1 and h OCT 2. This dye may be therefore useful for fluorimetrically investigating cellular h OCT 1 or h OCT 2 activity, knowing, however, that other factors potentially contributing to cellular accumulation of rhodamine 123, including mitochondrial membrane potential or expression of the efflux transporter P ‐glycoprotein, have also to be considered.