PMID: 9655880Jul 10, 1998Paper

Functional characterization of an organic cation transporter (hOCT1) in a transiently transfected human cell line (HeLa)

The Journal of Pharmacology and Experimental Therapeutics
L ZhangK M Giacomini

Abstract

Recently, a polyspecific organic cation transporter, hOCT1, was cloned from human liver. To date, limited studies examining the functional characteristics of the transporter have been performed. The purpose of the present study was to develop a mammalian expression system for hOCT1 and to characterize the interactions of various compounds with the cloned transporter. Lipofection was used to transiently transfect the hOCT1 plasmid DNA in a human cell line, HeLa. We tested the interaction of an array of organic cations and other compounds with hOCT1 by determining Ki values in inhibiting 14C-tetraethylammonium (TEA) transport in the transfected cells. Transient expression of hOCT1 activity was observed between 24 and 72 hr post-transfection, with maximal expression at approximately 40 hr. TEA transport was temperature dependent and saturable with Vmax and K(m) values of 2.89 +/- 0.448 nmol/mg protein/30 min and 229 +/- 78.4 microM, respectively. 14C-TEA uptake in hOCT1 plasmid DNA-transfected HeLa cells was trans-stimulated by unlabeled TEA and 1-methyl-4-phenyl-pyridinium. Organic cations, including clonidine, quinine, quinidine and verapamil (0.1 mM), significantly inhibited 14C-TEA uptake, whereas the organic anion, p-aminohip...Continue Reading

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