Basolateral phosphate transport in renal proximal-tubule-like OK cells.
It is generally assumed that phosphate (Pi) effluxes from proximal tubule cells by passive diffusion across the basolateral (BL) membrane. We explored the mechanism of BL Pi efflux in proximal tubule-like OK cells grown on permeable filters and then loaded with 32P. BL efflux of 32P was significantly stimulated (P < 0.05) by exposing the BL side of the monolayer to 12.5 mM Pi, to 10 mM citrate, or by acid-loading the cells, and was inhibited by exposure to 0.05 mM Pi or 25 mM HCO3; by contrast, BL exposure to high (8.4) pH, 40 mM K+, 140 mM Na gluconate (replacing NaCl), 10 mM lactate, 10 mM succinate, or 10 mM glutamate did not affect BL 32P efflux. These data are consistent with BL Pi efflux from proximal tubule-like cells occurring, in part, via an electro-neutral sodium-sensitive anion transporter capable of exchanging two moles of intracellular acidic H2PO4- for each mole of extracellular basic HPO4= or for citrate.
Department of Pediatrics, Albert Einstein College of Medicine, New York, New York, USA. mario@hsc.kuniv.edu.kw
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Barac-Nieto
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Alfred
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Spitzer
D000818:Animals; D000838:Anions / Q000378:metabolism; D001639:Bicarbonates / Q000494:pharmacology; D002118:Calcium / Q000494:pharmacology; D016764:Cell Polarity; D002478:Cells, Cultured / Q000187:drug effects / Q000378:metabolism; D002794:Choline / Q000494:pharmacology; D019343:Citric Acid / Q000494:pharmacology; D011756:Diphosphates / Q000494:pharmacology; D005942:Gluconates / Q000494:pharmacology; D005971:Glutamates / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D017136:Ion Transport / Q000187:drug effects*; D007687:Kidney Tubules, Proximal / Q000166:cytology* / Q000378:metabolism; D007773:Lactates / Q000494:pharmacology; D009893:Opossums; D028061:Phosphate Transport Proteins / Q000187:drug effects / Q000378:metabolism*; D010710:Phosphates / Q000378:metabolism*; D011189:Potassium Chloride / Q000494:pharmacology; D013386:Succinates / Q000494:pharmacology
D000838:Anions; D001639:Bicarbonates; D011756:Diphosphates; D005942:Gluconates; D005971:Glutamates; D007773:Lactates; D028061:Phosphate Transport Proteins; D010710:Phosphates; D013386:Succinates; D019343:Citric Acid; D011189:Potassium Chloride; D002794:Choline; C030691:gluconic acid; D002118:Calcium