22 research outputs found

    Localization and Functional Characterization of the Rat Oatp4c1 Transporter in an In Vitro Cell System and Rat Tissues

    Get PDF
    The organic anion transporting polypeptide 4c1 (Oatp4c1) was previously identified as a novel uptake transporter predominantly expressed at the basolateral membrane in the rat kidney proximal tubules. Its functional role was suggested to be a vectorial transport partner of an apically-expressed efflux transporter for the efficient translocation of physiological substrates into urine, some of which were suggested to be uremic toxins. However, our in vitro studies with MDCKII cells showed that upon transfection rat Oatp4c1 polarizes to the apical membrane. In this report, we validated the trafficking and function of Oatp4c1 in polarized cell systems as well as its subcellular localization in rat kidney. Using several complementary biochemical, molecular and proteomic methods as well as antibodies amenable to immunohistochemistry, immunofluorescence, and immunobloting we investigated the expression pattern of Oatp4c1 in polarized cell systems and in the rat kidney. Collectively, these data demonstrate that rat Oatp4c1 traffics to the apical cell surface of polarized epithelium and localizes primarily in the proximal straight tubules, the S3 fraction of the nephron. Drug uptake studies in Oatp4c1-overexpressing cells demonstrated that Oatp4c1-mediated estrone-3-sulfate (E3S) uptake was pH-dependent and ATP-independent. These data definitively demonstrate the subcellular localization and histological location of Oatp4c1 and provide additional functional evidence that reconciles expression-function reports found in the literature

    Discharge Coefficient of Small Submerged Orifices

    No full text

    Immunologic distribution of an organic anion transport protein in rat liver and kidney

    No full text
    A Na(+)-independent organic anion transport protein was recently cloned from rat liver using a Xenopus laevis oocyte expression system [E. Jacquemin, B. Hagenbuch, B. Stieger, A.W. Wolkoff, and P.J. Meier, Proc. Natl. Acad. Sci. USA 91: 133-137, 1994]. Although expression of this protein is sufficient for cells to transport the organic anion bromosulfophthalein, little is known about its cell biology or biochemical characteristics. Northern blot analysis performed under high-stringency conditions revealed hybridization with RNA only from liver and kidney; transcripts appeared the same in these two organs. Within kidney, hybridization was greatest when RNA extracted from the outer medulla was used. Immunoblot analysis revealed that in liver, the transporter was enriched in 0.1 M Na2CO3-extracted membranes and sinusoidal plasma membrane preparations, consistent with its being an integral membrane protein. This 80-kDa protein migrated as a 65-kDa protein after treatment with N-glycanase. Immunomorphological examination of liver revealed basolateral plasma membrane localization. In 0.1 M Na2CO3-extracted membranes of kidney, the transporter migrated as an 83-kDa protein on nonreducing sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). On reduction, it resolved into peptides of 33 and 37 kDa. SDS-PAGE migration of the liver protein was unaffected by reduction. Immunomorphological examination of kidney revealed apical plasma membrane localization in the S3 segment of the proximal tubule of the outer medulla. Differential processing and trafficking of this transporter in liver and kidney may have important functional and regulatory consequences
    corecore