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. 1999 Apr 13;257(2):289-94.
doi: 10.1006/bbrc.1999.0446.

Unidirectional Transport From Apical to Basolateral Compartment of Cobalt Ion in Polarized Madin-Darby Canine Kidney Cells

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Unidirectional Transport From Apical to Basolateral Compartment of Cobalt Ion in Polarized Madin-Darby Canine Kidney Cells

M Nagao et al. Biochem Biophys Res Commun. .

Abstract

Renal transport of Co2+ was studied by use of cultured MDCK cells with cell polarity. Cells imported 57Co2+ from the apical membrane exclusively, while uptake from the basolateral membrane was minute. Apical uptake was time-, concentration-, pH-, and temperature- dependent and the dose-dependency curve was saturable, indicating that a carrier-mediated influx process operates in the apical membrane. The substrate specificity and other properties of this Co2+ transport process are distinct from those of a transporter DCT1, divalent cation transporter 1, with unusually broad substrate specificity including Co2+. Radioactive Co2+ added from the apical side appeared in the basolateral side, while there was only slight movement of Co2+ from the basolateral to apical side, indicating that this unidirectional transepithelial passage of Co2+ is not caused by the paracellular diffusion, but by the basolateral export of the cellular Co2+ uptake from the apical membrane. Our results may indicate the presence of a novel vectorial transport system responsible for the reabsorption of Co2+ from the glomerular filtrate.

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