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  • Title: Mechanisms of transport of quinapril in Caco-2 cell monolayers: comparison with cephalexin.
    Author: Hu M, Zheng L, Chen J, Liu L, Zhu Y, Dantzig AH, Stratford RE.
    Journal: Pharm Res; 1995 Aug; 12(8):1120-5. PubMed ID: 7494822.
    Abstract:
    PURPOSE: To determine the transport mechanisms of quinapril and cephalexin in Caco-2 cell monolayers, a cell culture model of the human small intestinal epithelium. METHODS: Uptake, transepithelial transport and intracellular accumulations of these two drugs were measured using Caco-2 cell monolayers grown onto Millicells and magnetically stirred diffusion chambers. RESULTS: Transepithelial transport, apical (AP)4 uptake and intracellular accumulation of both drugs depended on the maintenance of a transepithelial proton gradient and temperature of the medium. However, quinapril transport and accumulation, which did not display a maximum at approximately pH 6, was more sensitive to proton gradient change, whereas cephalexin transport was more sensitive to concentration change (range 0.5-5 mM). In addition, quinapril (1 mM) transport was decreased significantly (p < 0.05) by 10 mM cephalexin, loracarbef, Gly-Pro and Phe-Pro, but not by enalapril; whereas cephalexin (0.1 mM) transport was decreased significantly (p < 0.05) by all four compounds. Similarly, AP quinapril (1 mM) uptake was also decreased by 10 mM loracarbef, Gly-Pro, cephalexin, and enalapril, but these inhibitory effects (20-50%) were quantitatively less than their inhibitory effects on cephalexin uptake (50-90%). Finally, the AP uptake of quinapril was also significantly (p < 0.05) inhibited by FCCP (10 micrograms/ml), amiloride (0.5 mM), DEP (0.5 mM), and staurosporine (5 nM). CONCLUSIONS: The transport of quinapril in the Caco-2 cells is via a combination of the carrier-mediated proton gradient-dependent peptide transporter and passive diffusion.
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