May 2004
Volume 45, Issue 13
ARVO Annual Meeting Abstract  |   May 2004
Functional Characterization of Brimonidine Transport in the Retinal Pigment Epithelium
Author Affiliations & Notes
  • N. Zhang
    Department of Pharmaceutical Sciences, School of Pharmacy, Univ of Southern California, Los Angeles, CA
  • D.R. Hinton
    Doheny Eye Institute and the Departments of Ophthalmology, Pathology, and Cell and Neurobiology, Keck School of Medicine, Univ of Southern California, Los Angeles, CA
  • Footnotes
    Commercial Relationships  N. Zhang, Allergan F; D.R. Hinton, Allergan F.
  • Footnotes
    Support  Arnold and Mabel Beckman Fundation
Investigative Ophthalmology & Visual Science May 2004, Vol.45, 3954. doi:
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      N. Zhang, D.R. Hinton; Functional Characterization of Brimonidine Transport in the Retinal Pigment Epithelium . Invest. Ophthalmol. Vis. Sci. 2004;45(13):3954.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract: : Purpose: To characterize brimonidine transport in the retinal pigment epithelium (RPE) Methods: The transport of [3H]brimonidine in bovine RPE–choroid explants was evaluated in a modified Ussing chamber. The basolateral and apical uptake or efflux of brimonidine was also evaluated in differentiated ARPE–19 cells cultured on permeable transwell filters. Results: Bovine RPE–choroid explants produced a trans–epithelial potential difference (PD) of 6.5 ± 0.6mV, and a trans–epithelial electrical resistance (TEER) of 260 ± 40 Ω.cm2. The apparent permeability coefficient for 10nM brimonidine in the choroidal–to–retinal (C to R) direction at 37oC was 1.7 times higher than that at 4oC. Brimonidine transport in the C to R direction showed concentration dependency over 0.01µM to 100µM with an apparent Michaelis–Menten constant of 51 ± 17 µM and a maximal flux of 148 ± 22 pmole/(cm2.h). After one month culture, ARPE–19 cell layer showed a TEER of 33 ± 2 Ω.cm2 with no detectable PD. Apical and basolateral uptake of 20nM brimonidine for 5min at 37oC in ARPE–19 cell mono–layers was 3.0 and 1.9 times greater than that at 4oC, respectively. Five–minute apical brimonidine efflux at 37oC was 5.6 times greater than that at 4oC, while brimonidine efflux at the basolateral side at 37oC showed no statistically significant difference from that at 4oC (p–value>0.1). Conclusion: The transport of brimonidine through the RPE in the choroidal–to–retinal direction is facilitated by a carrier–mediated system. This system might contribute to the fast absorption of brimonidine at the posterior region of the eye after topical application. Acknowledgement: We wish to thank Dr. Diane Tang–Liu(Allergan, CA) for providing brimonidine tartrate. This research is supported by the Arnold and Mabel Beckman Foundation.

Keywords: retinal pigment epithelium 

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