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GS Tirucherai, S Majumdar, AK Mitra; Mechanism of Ganciclovir Transport Across a Rabbit Corneal Epithelial Cell line (SIRC) and Intact Rabbit Cornea . Invest. Ophthalmol. Vis. Sci. 2002;43(13):1673.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose:To investigate the mechanism of corneal permeation of the antiviral compound ganciclovir (GCV) using a corneal epithelial cell line (SIRC) and intact rabbit cornea.Methods:Concentration, pH, and energy dependence of uptake of [3H] GCV was characterized using the SIRC cell line. Substrate specificity of the uptake process of [3H] GCV and [3H] adenine was also investigated. Permeation studies across intact rabbit cornea were performed at 34 deg. C using standard side-bi-side diffusion cells.Results:[3H] GCV uptake by SIRC, was found to comprise of a saturable (Km 1.29 ± 0.18 mM and Vmax 1.64 ± 0.36 nmoles/min/mg) and a non saturable (Kd 0.6506 ± 0.063 µl/min/mg) component. The uptake of GCV was found to be independent of pH, energy and sodium. Uptake studies using SIRC revealed the expression of a purine type nucleobase transporter with high affinity for adenine (Km 14.4 ± 2.3 µM, Vmax 0.4 ± 0.04 nmoles/min/mg and Kd 0.45 ± 0.02 µl/min/mg). Uptake of [3H] GCV was significantly inhibited by adenine indicating that GCV shared the nucleobase transporter. In studies using intact rabbit cornea it was observed that although unlabeled adenine greatly reduced the transport of [3H] adenine, the rate of [3H] GCV transport was unaffected. The permeability values of GCV across the rabbit cornea at various concentrations of GCV remained constant.Conclusion:The expression of a purine-specific nucleobase transporter in the SIRC cell line and rabbit cornea was clearly demonstrated. Although the nucleobase transporter is involved in the uptake of GCV by the corneal epithelium, the net permeation of GCV across intact rabbit cornea occurs by passive diffusion.
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