Unidirectional transport from apical to basolateral compartment of cobalt ion in polarized Madin-Darby canine kidney cells.
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.
Nagao
M
M
Graduate School of Agriculture, Kyoto University, Kyoto, 606-8502, Japan.
Sugaru
E
E
Kambe
T
T
Sasaki
R
R
D000818:Animals; D001667:Binding, Competitive; D001692:Biological Transport / Q000187:drug effects; D002352:Carrier Proteins / Q000378:metabolism; D027682:Cation Transport Proteins; D002412:Cations / Q000378:metabolism* / Q000494:pharmacology; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D016764:Cell Polarity; D003035:Cobalt / Q000378:metabolism*; D004285:Dogs; D004305:Dose-Response Relationship, Drug; D004847:Epithelial Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D033862:Iron-Binding Proteins; D007668:Kidney / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism; D008670:Metals / Q000494:pharmacology; D019810:Sodium Azide / Q000494:pharmacology; D013379:Substrate Specificity; D013696:Temperature; D013997:Time Factors; D015032:Zinc / Q000378:metabolism / Q000494:pharmacology; D000099236:Solute Carrier Family 11, Member 2
D002352:Carrier Proteins; D027682:Cation Transport Proteins; D002412:Cations; D003035:Cobalt; D033862:Iron-Binding Proteins; D008565:Membrane Proteins; D008670:Metals; D019810:Sodium Azide; D015032:Zinc; D000099236:Solute Carrier Family 11, Member 2