Functional characterization of mouse cation transporter mOCT2 compared with mOCT1.
We characterized the function of mouse organic cation transporter OCT2 (TC 2.A.19.1.5) in comparison with that of OCT1 (TC 2.A.19.1.1). Uptake of [(3)H]1-methyl-4-phenylpyridinium ([(3)H]MPP(+)) by Xenopus laevis oocytes injected with mOCT1 (Slc22a1) or mOCT2 (Slc22a2) cRNA was attenuated by an increase of extracellular K(+) concentration and under acidic extracellular conditions. The uptakes of [(3)H]MPP(+) via mOCT1 and mOCT2 were saturable, with similar Michaelis constants (K(t)) of 10 and 24 microM, respectively. mOCT2 also mediated the uptake of [(14)C]tetraethylammonium with a K(t) value of 36 microM, which is similar to that of mOCT1. Quinine, tetraethylammonium, cimetidine, procainamide, choline, and N(')-methylnicotinamide inhibited the uptake of [(3)H]MPP(+) via mOCT1, as well as via mOCT2, and the inhibitory potencies for mOCT1 were comparable to but slightly higher than those for mOCT2. Thus, although the transport properties of mOCT2 are similar to those of mOCT1 in respect to the membrane-potential dependency, pH-sensitivity, and affinities for MPP(+) and tetraethylammonium, several organic cations had weaker inhibitory effects on [(3)H]MPP(+) uptake by mOCT2 than by mOCT1.
Kakehi
Mari
M
Department of Medico-Pharmaceutical Sciences, Graduate School of Pharmaceutical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan.
Koyabu
Noriko
N
Nakamura
Takanori
T
Uchiumi
Takeshi
T
Kuwano
Michihiko
M
Ohtani
Hisakazu
H
Sawada
Yasufumi
Y
D015655:1-Methyl-4-phenylpyridinium / Q000378:metabolism; D000818:Animals; D001483:Base Sequence; D001692:Biological Transport; D002412:Cations / Q000494:pharmacology; D002478:Cells, Cultured; D003001:Cloning, Molecular; D004305:Dose-Response Relationship, Drug; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008564:Membrane Potentials; D051379:Mice; D027701:Organic Cation Transport Proteins / Q000235:genetics / Q000378:metabolism*; D027702:Organic Cation Transporter 1 / Q000235:genetics / Q000378:metabolism*; D000075102:Organic Cation Transporter 2; D019789:Tetraethylammonium / Q000378:metabolism; D014981:Xenopus
D002412:Cations; D027701:Organic Cation Transport Proteins; D027702:Organic Cation Transporter 1; D000075102:Organic Cation Transporter 2; C491012:Slc22a2 protein, mouse; D019789:Tetraethylammonium; D015655:1-Methyl-4-phenylpyridinium