L S Gan1, S Yanni, D R Thakker. 1. Department of Drug Metabolism, Glaxo Inc., Research Triangle Park, North Carolina 27709, USA.
Abstract
PURPOSE: The tight junctions in the intestinal epithelium represent highly specialized intercellular junctions. Ranitidine, an H2-antagonist, causes a tightening of the tight junctions. Hence, we have investigated the effect of ranitidine and other H2-antagonists on the function of the intestinal tight junctions. METHODS: Effect of the H2-antagonists on the tight junctions has been investigated using the transepithelial electrical resistance (TEER) and the transport of mannitol across the Caco-2 cell monolayers. RESULTS: Four different H2-antagonists caused an increase in the TEER across the Caco-2 cell monolayers, accompanied by a decrease in the permeability for mannitol. The effect was concentration-dependent and saturable. Ranitidine and famotidine, caused a decrease in their own transport rate across the Caco-2 cells. Ranitidine competitively inhibited the increase in TEER caused by famotidine, whereas compounds which represent molecular fragments of ranitidine had no effect. The relative potency of the four H2-antagonists in causing an increase in the TEER correlated inversely with the oral bioavailability of these compounds in humans. CONCLUSIONS: We hypothesize that the H2-antagonists exert their effect on the tight junctions of Caco-2 cells by modulation of interactions among proteins associated with the tight junctional complex.
PURPOSE: The tight junctions in the intestinal epithelium represent highly specialized intercellular junctions. Ranitidine, an H2-antagonist, causes a tightening of the tight junctions. Hence, we have investigated the effect of ranitidine and other H2-antagonists on the function of the intestinal tight junctions. METHODS: Effect of the H2-antagonists on the tight junctions has been investigated using the transepithelial electrical resistance (TEER) and the transport of mannitol across the Caco-2 cell monolayers. RESULTS: Four different H2-antagonists caused an increase in the TEER across the Caco-2 cell monolayers, accompanied by a decrease in the permeability for mannitol. The effect was concentration-dependent and saturable. Ranitidine and famotidine, caused a decrease in their own transport rate across the Caco-2 cells. Ranitidine competitively inhibited the increase in TEER caused by famotidine, whereas compounds which represent molecular fragments of ranitidine had no effect. The relative potency of the four H2-antagonists in causing an increase in the TEER correlated inversely with the oral bioavailability of these compounds in humans. CONCLUSIONS: We hypothesize that the H2-antagonists exert their effect on the tight junctions of Caco-2 cells by modulation of interactions among proteins associated with the tight junctional complex.
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