title: Modification of the internal pH sensitivity of the Na+/H+ antiporter by parathyroid hormone in a cultured renal cell line.
abstract: Sodium-proton antiporter activity can be modulated through changes Vmax and/or intracellular proton sensitivity of the antiporter. To characterize a parathyroid hormone (PTH)-induced decrease in antiporter activity in a continuous renal cell line (opossum kidney cells), the extracellular sodium and intracellular proton dependence of amiloride-inhibitable 22Na uptake was studied. The Km for extracellular sodium at intracellular pH 6.32 was 28 mM and was unaltered by PTH, whereas the Vmax was decreased by 26%. When intracellular pH was set over the range 5.87-7.57 by the potassium-nigericin method, antiporter activity increased as intracellular pH decreased. Hill analysis revealed Hill coefficients of 1.25 and 1.01 and half-maximal antiporter activity at intracellular pH values of 6.90 and 6.35 for control and PTH-treated cells, respectively. PTH decreased the apparent Vmax at low pH by 15% and the intracellular pH at which Na+/H+ exchange is half-maximal by 0.55 pH units.
mesh_terms: D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism*; D002460:Cell Line; D002478:Cells, Cultured; D006863:Hydrogen-Ion Concentration; D007668:Kidney / Q000187:drug effects* / Q000378:metabolism; D007700:Kinetics; D008433:Mathematics; D010281:Parathyroid Hormone / Q000494:pharmacology*; D011188:Potassium / Q000494:pharmacology; D017923:Sodium-Hydrogen Exchangers
chemical_list: D002352:Carrier Proteins; D010281:Parathyroid Hormone; D017923:Sodium-Hydrogen Exchangers; D011188:Potassium