title: Vectorial bicarbonate transport by Par-C10 salivary cells.
abstract: Salivary glands produce a HCO(3)(-)-rich fluid that is important for the neutral milieu in the upper gastrointestinal tract. The molecular mechanism of this secretion is poorly understood. Par-C10, an immortalized rat parotid acinar line, has been shown to secrete Cl(-)- in response to Ca(2+-)-mobilizing stimuli. Our aim was to assess the capacity of polarized monolayers of Par-C10 cells to transport and secrete HCO(3)(-)-. Transepithelial electrolyte movement was evaluated by short-circuit current measurements. Intracellular pH (pH(i)) was measured by microfluorometry in cells loaded with BCECF. Monolayers of Par-C10 cells, grown on Transwell membranes, developed high transepithelial resistance and exhibited vectorial anion secretion which was activated by both ATP and forskolin. The currents were partially inhibited by bumetanide and by withdrawal of HCO(3)(-) indicating the dependence of ion movements on NKCC and on HCO(3)(-) ions, respectively. In HCO(3)(-)-free solutions the recovery of pH(i) from acid loading was abolished by EIPA. In the presence of HCO(3)(-) there was a strong EIPA-insensitive recovery from acid loading which was inhibited by H(2)DIDS. ATP and forskolin stimulated HCO(3)(-) efflux from the cells. Furthermore, HCl(-) withdrawal experiments showed the presence of DNDS-sensitive basolateral anion exchange. In conclusion Par-C10 cells achieve transepithelial transport that is sensitive to both intracellular Ca(2+)- and cAMP-dependent stimulation. We identified Na(+)/H(+) exchange, Na(+)-HCO(3)(-) cotransport and anion exchange at the basolateral side of the cells as being involved in intracellular pH regulation and vectorial HCO(3)(-) secretion. This cell line offers a good model for further studies to understand the molecular mechanisms of salivary HCO(3)(-) secretion.
authors.affiliation: Molecular Oral Biology Research Group, Department of Oral Biology, Semmelweis University, Budapest, Hungary.
authors.forename: I
authors.initials: I
authors.lastname: Demeter
authors.forename: A
authors.initials: A
authors.lastname: Szucs
authors.forename: O
authors.initials: O
authors.lastname: Hegyesi
authors.forename: A
authors.initials: A
authors.lastname: Foldes
authors.forename: G Z
authors.initials: GZ
authors.lastname: Racz
authors.forename: B
authors.initials: B
authors.lastname: Burghardt
authors.forename: M C
authors.initials: MC
authors.lastname: Steward
authors.forename: G
authors.initials: G
authors.lastname: Varga
mesh_terms: D000136:Acid-Base Equilibrium / Q000502:physiology; D000255:Adenosine Triphosphate / Q000494:pharmacology; D000262:Adenylyl Cyclases / Q000378:metabolism; D000818:Animals; D027321:Anion Transport Proteins / Q000378:metabolism; D017920:Antiporters / Q000378:metabolism; D001639:Bicarbonates / Q000378:metabolism*; D020013:Calcium Signaling / Q000187:drug effects; D002460:Cell Line; D016764:Cell Polarity / Q000502:physiology*; D027963:Chloride-Bicarbonate Antiporters / Q000037:antagonists & inhibitors; D000242:Cyclic AMP / Q000378:metabolism; D017097:Electric Impedance; D006863:Hydrogen-Ion Concentration; D017136:Ion Transport; D049990:Membrane Transport Modulators / Q000494:pharmacology; D010306:Parotid Gland / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D051381:Rats; D064606:SLC4A Proteins; D012469:Salivary Glands / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D015398:Signal Transduction / Q000187:drug effects; D049994:Sodium Potassium Chloride Symporter Inhibitors / Q000494:pharmacology; D027982:Sodium-Bicarbonate Symporters / Q000037:antagonists & inhibitors; D000074082:Sodium-Hydrogen Exchanger 1; D017923:Sodium-Hydrogen Exchangers / Q000037:antagonists & inhibitors; D028021:Sodium-Potassium-Chloride Symporters / Q000378:metabolism; D064466:Solute Carrier Family 12, Member 1
chemical_list: D027321:Anion Transport Proteins; D017920:Antiporters; D001639:Bicarbonates; D027963:Chloride-Bicarbonate Antiporters; D049990:Membrane Transport Modulators; D064606:SLC4A Proteins; C578716:Slc12a1 protein, rat; C422004:Slc4a4 protein, rat; C452850:Slc9a1 protein, rat; D049994:Sodium Potassium Chloride Symporter Inhibitors; D027982:Sodium-Bicarbonate Symporters; D000074082:Sodium-Hydrogen Exchanger 1; D017923:Sodium-Hydrogen Exchangers; D028021:Sodium-Potassium-Chloride Symporters; D064466:Solute Carrier Family 12, Member 1; D000255:Adenosine Triphosphate; D000242:Cyclic AMP; D000262:Adenylyl Cyclases