The organic cation transporter OCT2 mediates the uptake of beta-adrenoceptor antagonists across the apical membrane of renal LLC-PK(1) cell monolayers

Br J Pharmacol. 2000 Sep;131(1):71-9. doi: 10.1038/sj.bjp.0703518.

Abstract

Previous studies have shown that beta-adrenoceptor antagonists may be substrates of organic cation transporters in kidney and lung. In this study we examined the transport of the beta-adrenoreceptor antagonists propranolol and metoprolol, in renal LLC-PK(1) cell monolayers. Experiments with BCECF (2', 7'-bis(2carboxyethyl)-5(6)-carboxyfluorescein) loaded LLC-PK(1) cell monolayers demonstrated that metoprolol and propranolol flux across the basolateral membrane was consistent with non-ionic diffusion. Flux across the apical membrane consisted of both non-ionic diffusion and the uptake of the cationic form of the beta-adrenoceptor antagonists. Uptake of the cationic form of metoprolol across the apical membrane was Na(+)-independent, electrogenic and sensitive to external pH. Furthermore, uptake was sensitive to inhibition by Decynium-22 and the organic cations TEA (tetraethylammonium) and MPP(+) (1-methyl 4-phenylpyridinium). These results, allied with the apical location of the uptake mechanism suggest that beta-adrenoceptor antagonists may be substrates for the organic cation transporter, OCT2. To confirm beta-adrenoceptor antagonists as substrates for OCT2, we demonstrate, in cells transiently transfected with an epitope tagged version of hOCT2 (hOCT2-V5):(1) Decynium-22 sensitive [(14)C]-propranolol uptake, (2) cis-inhibition of OCT2 by a range of beta-adrenoceptor antagonists and (3) metoprolol induced intracellular acidification.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adrenergic beta-Antagonists / pharmacokinetics*
  • Biological Transport
  • Carrier Proteins / physiology*
  • Cells, Cultured
  • Cimetidine / pharmacokinetics
  • Hydrogen-Ion Concentration
  • Kidney / cytology
  • Kidney / metabolism*
  • Metoprolol / pharmacokinetics
  • Metoprolol / pharmacology
  • Organic Cation Transport Proteins*
  • Organic Cation Transporter 2
  • Propranolol / pharmacokinetics
  • Quinolines / pharmacology

Substances

  • Adrenergic beta-Antagonists
  • Carrier Proteins
  • Organic Cation Transport Proteins
  • Organic Cation Transporter 2
  • Quinolines
  • Slc22a2 protein, rat
  • pseudoisocyanine
  • Cimetidine
  • Propranolol
  • Metoprolol