Pharmaceutical Research

, Volume 22, Issue 1, pp 113–121 | Cite as

A Fluorometric Screening Assay for Drug Efflux Transporter Activity in the Blood-Brain Barrier


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To examine the capability of a fluorometric assay to identify and characterize the drug efflux interactions of a broad spectrum of drug agents in an in vitro model of the blood-brain barrier (BBB).


Various concentrations of drug agent (1, 10, and 100 μM) were evaluated for their effect on the cellular accumulation of the P-glycoprotein (P-gp) probe R123 (3.2 μM), and the mixed P-gp and multidrug resistance-associated protein (MRP) probe, BCECF (1 μM), in bovine brain microvessel endothelial cell (BBMEC) monolayers. Drugs demonstrating a significant effect were further quantitated using an expanded concentration range and a nonlinear regression curve fit to determine the potency (IC50) and efficacy (Imax) of the drug for P-gp and/or MRP.


Several of the 36 therapeutic agents examined showed drug efflux transporter interactions in BBMEC monlayers. Melphalan and risperidone significantly enhanced the accumulation of R123 over control (1.47- and 1.82-fold, respectively) with resulting IC50s of 1.4 and 14.6 μM, respectively. Chlorambucil and valproic acid significantly enhanced the accumulation of BCECF compared to control monolayers (2.02- and 4.01-fold, respectively) with resulting IC50s of 146.1 and 768.5 μM, respectively.


The current study demonstrates the feasibility of a fluorometric assay consisting of R123 and BCECF in assessing the drug efflux interactions of a variety of drugs in the BBB.

Key words:

BCECF blood-brain barrier MRP P-gp 


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© Springer Science+Business Media, Inc. 2005

Authors and Affiliations

  1. 1.Department of Pharmaceutical SciencesUniversity of Nebraska Medical CenterOmahaUSA

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