title: The biphasic calcium dose-response curve for parathyroid hormone secretion in electropermeabilized adult bovine parathyroid cells.
abstract: We have used the method of electropermeabilization to measure the dependence of PTH secretion on internal calcium concentration in adult bovine parathyroid cells. The dose-response curve is biphasic, with a peak at 10(-7) M calcium. This result differs significantly from the dose-response curves that have been determined by this method for many other secretory systems, where secretion requires much more calcium and the dependence of secretion on calcium is monotonic. Guanine nucleotide analogs did not modify the calcium dose-response curve of PTH secretion in the electropermeabilized parathyroid cells. The unique properties of adult parathyroid cell secretion are analogous to the unique properties of parathyroid calcium-activated potassium channels, which differ from calcium-activated potassium channels of other cells in that they open at unusually low calcium concentrations and have a peak open probability at about 10(-7) M calcium. We suggest that the opening of these channels in secretory vesicles is required for secretion.
authors.affiliation: Laboratory of Biophysics, National Institute of Neurological Disorders and Stroke, Bethesda, Maryland 20892.
authors.forename: S L
authors.initials: SL
authors.lastname: Pocotte
authors.forename: G
authors.initials: G
authors.lastname: Ehrenstein
mesh_terms: D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000494:pharmacology*; D002417:Cattle; D002463:Cell Membrane Permeability; D002478:Cells, Cultured; D002712:Chlorides / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D006160:Guanosine Triphosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D007700:Kinetics; D010280:Parathyroid Glands / Q000187:drug effects / Q000378:metabolism*; D010281:Parathyroid Hormone / Q000378:metabolism*; D012413:Rubidium / Q000378:metabolism; D013873:Thionucleotides / Q000494:pharmacology
chemical_list: D002712:Chlorides; D010281:Parathyroid Hormone; D013873:Thionucleotides; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D006160:Guanosine Triphosphate; D000255:Adenosine Triphosphate; D012413:Rubidium; C032710:rubidium chloride; D002118:Calcium