Endogenous expression of the renal high-affinity H+-peptide cotransporter in LLC-PK1 cells |
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Authors: | Wenzel, Uwe Diehl, Daniela Herget, Martina Daniel, Hannelore |
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Abstract: | The reabsorption of filtered di- andtripeptides as well as certain peptide mimetics from the tubular lumeninto renal epithelial cells is mediated by anH+-coupledhigh-affinity transport process. Here we demonstrate for the first timeH+-coupled uptake of dipeptidesinto the renal proximal tubule cell lineLLC-PK1. Transport was assessed1) by uptake studies using theradiolabeled dipeptideD-[3H]Phe-L-Ala,2) by cellular accumulation of the fluorescent dipeptide D-Ala-Lys-AMCA, and3) by measurement of intracellularpH (pHi) changes as aconsequence of H+-coupleddipeptide transport. Uptake ofD-Phe-L-Alaincreased linearly over 11 days postconfluency and showed all thecharacteristics of the kidney cortex high-affinity peptide transporter,e.g., a pH optimum for transport ofD-Phe-L-Alaof 6.0, an apparent Km value forinflux of 25.8 ± 3.6 µM, and affinities of differently chargeddipeptides or the -lactam antibiotic cefadroxil to the binding sitein the range of 20-80 µM.pHi measurements established thepeptide transporter to induce pronounced intracellular acidification inLLC-PK1 cells and confirm itspostulated role as a cellular acid loader. |
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