Yoshiyuki Kubo1, Ayumi Nakazawa1, Shin-Ichi Akanuma1, Ken-Ichi Hosoya2. 1. Department of Pharmaceutics, Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama, 2630, Sugitani, Toyama, 930-0194, Japan. 2. Department of Pharmaceutics, Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama, 2630, Sugitani, Toyama, 930-0194, Japan. hosoyak@pha.u-toyama.ac.jp.
Abstract
PURPOSE: To investigate the blood-to-retina verapamil transport at the blood-retinal barrier (BRB). METHODS: EverFluor FL Verapamil (EFV) was adopted as the fluorescent probe of verapamil, and its transport across the BRB was investigated with common carotid artery infusion in rats. EFV transport at the inner and outer BRB was investigated with TR-iBRB2 cells and RPE-J cells, respectively. RESULTS: The signal of EFV was detected in the retinal tissue during the weak signal of cell impermeable compound. In TR-iBRB2 cells, the localization of EFV differed from that of LysoTracker® Red, a lysosomotropic agent, and was not altered by acute treatment with NH4Cl. In RPE-J cells, the punctate distribution of EFV was partially observed, and this was reduced by acute treatment with NH4Cl. EFV uptake by TR-iBRB2 cells was temperature-dependent and membrane potential- and pH-independent, and was significantly reduced by NH4Cl treatment during no significant effect obtained by different extracellular pH and V-ATPase inhibitor. The EFV uptake by TR-iBRB2 cells was inhibited by cationic drugs, and inhibited by verapamil in a concentration-dependent manner with an IC50 of 98.0 μM. CONCLUSIONS: Our findings provide visual evidence to support the significance of carrier-mediated transport in the blood-to-retina verapamil transport at the BRB.
PURPOSE: To investigate the blood-to-retina verapamil transport at the blood-retinal barrier (BRB). METHODS:EverFluor FL Verapamil (EFV) was adopted as the fluorescent probe of verapamil, and its transport across the BRB was investigated with common carotid artery infusion in rats. EFV transport at the inner and outer BRB was investigated with TR-iBRB2 cells and RPE-J cells, respectively. RESULTS: The signal of EFV was detected in the retinal tissue during the weak signal of cell impermeable compound. In TR-iBRB2 cells, the localization of EFV differed from that of LysoTracker® Red, a lysosomotropic agent, and was not altered by acute treatment with NH4Cl. In RPE-J cells, the punctate distribution of EFV was partially observed, and this was reduced by acute treatment with NH4Cl. EFV uptake by TR-iBRB2 cells was temperature-dependent and membrane potential- and pH-independent, and was significantly reduced by NH4Cl treatment during no significant effect obtained by different extracellular pH and V-ATPase inhibitor. The EFV uptake by TR-iBRB2 cells was inhibited by cationic drugs, and inhibited by verapamil in a concentration-dependent manner with an IC50 of 98.0 μM. CONCLUSIONS: Our findings provide visual evidence to support the significance of carrier-mediated transport in the blood-to-retina verapamil transport at the BRB.
Authors: Faraz Kazmi; Tiffini Hensley; Chad Pope; Ryan S Funk; Greg J Loewen; David B Buckley; Andrew Parkinson Journal: Drug Metab Dispos Date: 2013-02-01 Impact factor: 3.922