Cloning and characterization of a potential-sensitive organic cation transporter (OCT3) from rat placenta

R. Kekuda, P. D. Prasad, X. Wu, F. H. Leibach, V. Ganapathy

Research output: Contribution to journalArticlepeer-review


We have cloned a cDNA from a rat placental cDNA library which, when expressed in mammalian cells, mediates the transport of the organic cations tetraethylammonium, methylphenylpyridinium and guanidine. The cDNA-mediated transport, when studied in intact cells, is influenced by extracellular pH, the transport activity being higher at alkaline pH compared to acidic pH. Several other organic cations including N-methylnicotinamide, dimethylamiloride, nicotine, cimetidine, clonidine, and methylphenyltetrahydropyridine are also substrates for this transporter. The cloned transporter can also be expressed functionally in X. laevis oocytes by injection of cRNA. When studied under voltage-clamp conditions, the transporter activity is associated with inward currents, indicative of transfer of positive charge into the oocyte. The influence of external pH is negligible under these voltage-clamp conditions. The cDNA is 3,502 bp long and contains an open reading frame coding for a protein of 551 amino acids. This transporter is distinct from the recently cloned potential-sensitive organic cation transporters OCT1 and OCT2 and is also distinct from the kidney-specific NKT, a putative organic cation transporter. Northern blot analysis indicates that the transporter-specific mRNA is abundantly expressed in the placenta and moderately expressed in the brain, kidney, heart, lung, and intestine. The expression is not detectable in the liver.

Original languageEnglish (US)
Pages (from-to)A1043
JournalFASEB Journal
Issue number5
StatePublished - Mar 20 1998

ASJC Scopus subject areas

  • Biotechnology
  • Biochemistry
  • Molecular Biology
  • Genetics


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