title: Sodium-phosphate cotransport in OK cells: inhibition by PTH and "adaptation" to low phosphate.
abstract: Sodium-phosphate (Na-Pi) cotransport is principally regulated by parathyroid hormone (PTH) and by the intrinsic ability to "adapt" to ambient phosphate concentration. In the present study, these two control mechanisms were examined in a cloned opossum kidney (OK) cell line. PTH inhibited Na-Pi cotransport, half-maximal inhibition at 5 x 10(-12) M, by fractionally similar amounts irrespective of the initial transport rates predetermined by "adaptation" to media phosphate concentration. At maximal concentrations of PTH (10(-8) M), the residual Na-Pi cotransport activity was higher in cells exposed to low-phosphate media. Cells preexposed to PTH (10(-8) M) or dibutyryl adenosine 3'-5'-cyclic monophosphate (DBcAMP) (10(-5) M) and forskolin (10(-5) M) increase transport (adaptation) by fractionally similar amounts as control cells for any given external phosphate concentration. The protein kinase C inhibitor, staurosporine, prevented PTH action but did not alter the ability to adapt Na-Pi cotransport in response to low media phosphate concentration. These data support the notion that regulation of Na-Pi cotransport by PTH and the adaptive response to available media phosphate concentration are distinct regulatory control mechanisms.
authors.affiliation: Department of Medicine, University of British Columbia, Vancouver, Canada.
authors.forename: G
authors.initials: G
authors.lastname: Quamme
authors.forename: J
authors.initials: J
authors.lastname: Biber
authors.forename: H
authors.initials: H
authors.lastname: Murer
mesh_terms: D000470:Alkaloids / Q000494:pharmacology; D000818:Animals; D003994:Bucladesine / Q000494:pharmacology; D002352:Carrier Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D002460:Cell Line; D005576:Colforsin / Q000494:pharmacology; D007668:Kidney / Q000187:drug effects / Q000378:metabolism; D007700:Kinetics; D010281:Parathyroid Hormone / Q000494:pharmacology*; D010446:Peptide Fragments / Q000494:pharmacology*; D010710:Phosphates / Q000378:metabolism*; D050608:Sodium-Phosphate Cotransporter Proteins; D019311:Staurosporine; D027981:Symporters; D019379:Teriparatide; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
chemical_list: D000470:Alkaloids; D002352:Carrier Proteins; D010281:Parathyroid Hormone; D010446:Peptide Fragments; D010710:Phosphates; D050608:Sodium-Phosphate Cotransporter Proteins; D027981:Symporters; D019379:Teriparatide; D005576:Colforsin; D003994:Bucladesine; D019311:Staurosporine; D013755:Tetradecanoylphorbol Acetate