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Publications (3)7.54 Total impact

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    ABSTRACT: Aims The purpose of this study was to clarify the expression and function of peptide transporter 2 (PEPT2) in primary cultured alveolar type II epithelial cells and in transdifferentiated type I-like cells. Main methods Real-time PCR analysis, uptake study of [(3)H]Gly-Sar, and immunostaining were performed in alveolar epithelial cells. Key findings The expression of PEPT2 mRNA in type II cells isolated from rat lungs was highest at day 0, and decreased rapidly during culture of the cells. In accordance with this change, PEPT2 activity estimated as cefadroxil-sensitive [(3)H]Gly-Sar uptake also decreased along with transdifferentiation. The expression of PEPT2 protein in type II cells was confirmed by immunostaining and Western blot analysis. The uptake of [(3)H]Gly-Sar in type II cells was time- and pH-dependent. In contrast, minimal time-dependence and no pH-dependence of [(3)H]Gly-Sar uptake were observed in type I-like cells. The maximal [(3)H]Gly-Sar uptake was observed at pH6.0, and the uptake decreased at higher pHs in type II cells. The uptake of [(3)H]Gly-Sar in type II cells was inhibited by cefadroxil in a concentration-dependent manner, the IC50 value being 4.3μM. On the other hand, no significant inhibition by cefadroxil was observed in type I-like cells. In addition, [(3)H]Gly-Sar uptake in type II cells was saturable, the Km value being 72.0μM. Significance PEPT2 is functionally expressed in alveolar type II epithelial cells, but the expression decreases along with transdifferentiation, and PEPT2 would be almost completely lost in type I cells.
    Life sciences 08/2013; · 2.56 Impact Factor
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    ABSTRACT: The mechanism underlying the handling of protein and peptide drugs such as insulin in alveolar epithelial cells is still unclear. We therefore examined fluorescein isothiocyanate-labeled (FITC)-insulin uptake in rat primary cultured alveolar type II epithelial cells and in transdifferentiated type I-like cells. FITC-insulin uptake in these cells was much higher than those of FITC-immunoglobulin (IgG), transferrin, and dextran. FITC-insulin uptake was time- and concentration-dependent, and was almost completely inhibited by metabolic inhibitors in both cells, while bafilomycin A(1) inhibited the uptake only in type II cells. Inhibitors of clathrin- and caveolae-mediated endocytosis did not affect FITC-insulin uptake in either type of cell. Dynasore, a dynamin GTPase inhibitor, potently inhibited FITC-insulin uptake in type II cells. These results suggest that the characteristics of insulin uptake in type II and type I cells are different, and dynamin-dependent endocytosis that utilizes neither clathrin nor caveolae is involved in type II cells, while a dynamin-independent pathway is mainly involved in type I cells.
    Biological & Pharmaceutical Bulletin 10/2009; 32(10):1765-9. · 1.85 Impact Factor
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    ABSTRACT: Effect of ursodeoxycholic acid (UDCA) treatment on the expression and function of intestinal multidrug resistance-associated protein (Mrp) 2 was examined in rats. When rats were orally administered 0.5% UDCA solution for 6 days, mRNA and protein levels of Mrp2 in the intestine were increased about twofold compared with those in untreated rats. In in vitro everted sac study, Mrp2-mediated efflux of 2,4-dinitrophenyl-S-glutathione (DNP-SG) to the mucosal surface was shown to be increased by UDCA treatment. In vivo intestinal exsorption clearance of DNP-SG was also increased by UDCA treatment. In addition, in situ intestinal absorption of methotrexate, a substrate of Mrp2, was decreased by the treatment. These results indicate that the expression and function of intestinal Mrp2 is up-regulated by oral administration of UDCA.
    Journal of Pharmaceutical Sciences 01/2009; 98(8):2822-31. · 3.13 Impact Factor