Pharmaceutical Research

, Volume 30, Issue 3, pp 847–856 | Cite as

Involvement of a Novel Organic Cation Transporter in Verapamil Transport Across the Inner Blood-Retinal Barrier

  • Yoshiyuki Kubo
  • Yusuke Kusagawa
  • Masanori Tachikawa
  • Shin-ichi Akanuma
  • Ken-ichi Hosoya
Research Paper



To clarify the transport and inhibition characteristics involved in verapamil transport across the inner blood-retinal barrier (inner BRB).


The transport of [3H]verapamil across the inner BRB was investigated using retinal uptake index and integration plot analyses in rats. The detailed transport characteristics were studied using TR-iBRB2 cells, a conditionally immortalized rat retinal capillary endothelial cell line that is an in vitro model of the inner BRB.


The apparent influx permeability clearance of [3H]verapamil was 614 μL/(min·g retina), which is 4.7-fold greater than that of brain. The retinal uptake of [3H]verapamil was slightly increased by 3 mM verapamil and 10 mM qunidine and inhibited by 40 mM pyrilamine, supporting the carrier-mediated efflux and influx transport of verapamil across the inner BRB. TR-iBRB2 cells exhibited a concentration-dependent uptake of [3H]verapamil with a Km of 61.9 μM, and the uptake was inhibited by several cations, such as pyrilamine, exhibiting a different profile from the identified transporters. These transport properties suggest that verapamil transport at the inner BRB takes place via a novel organic cation transporter.


Our findings suggest that a novel organic cation transporter is involved in verapamil transport from the blood to the retina across the inner BRB.


inner blood-retinal barrier lipophilic basic drug organic cation transporter P-glycoprotein 

Supplementary material

11095_2012_926_MOESM1_ESM.doc (1.1 mb)
ESM 1(DOC 1124 kb)


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Copyright information

© Springer Science+Business Media New York 2012

Authors and Affiliations

  • Yoshiyuki Kubo
    • 1
  • Yusuke Kusagawa
    • 1
  • Masanori Tachikawa
    • 1
    • 2
  • Shin-ichi Akanuma
    • 1
  • Ken-ichi Hosoya
    • 1
  1. 1.Department of Pharmaceutics Graduate School of Medicine and Pharmaceutical SciencesUniversity of ToyamaToyamaJapan
  2. 2.Division of Membrane Transport and Drug Targeting Graduate School of Pharmaceutical SciencesTohoku UniversitySendaiJapan

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