title: Expression of a sodium bicarbonate cotransporter in human parotid salivary glands.
abstract: The human parotid gland secretes much of the bicarbonate that enters the mouth. Prompted by studies of animal models, this study sought evidence for the expression of a functional Na(+)-HCO(3)(-) cotransporter (NBC) in human parotid acinar cells. Microfluorometric measurements of intracellular pH in isolated acini showed that the recovery from an acid load was achieved in part by HCO(3)(-) uptake via a Na(+)-dependent, DIDS-sensitive mechanism. By reverse transcriptase-polymerase chain reaction, a full-length NBC1 clone was obtained showing more than 99% homology with the human pancreatic isoform hpNBC1. Expressed in Xenopus oocytes, the electrogenicity of the transporter was detected as an inwardly directed, Na(+)- and HCO(3)(-)-dependent flux of negative charge. Immunohistochemistry using antibodies raised to NBC1 showed strong staining of the basolateral membrane of the acinar cells. Therefore, it was concluded that a functional electrogenic Na(+)-HCO(3)(-) cotransporter is expressed in the human parotid gland, and that it contributes to pH regulation in the acinar cells and could play a significant part in salivary secretion.
authors.affiliation: School of Biological Sciences, University of Manchester, G.38 Stopford Building, M13 9PT, Manchester, UK.
authors.forename: K
authors.initials: K
authors.lastname: Park
authors.forename: P T
authors.initials: PT
authors.lastname: Hurley
authors.forename: E
authors.initials: E
authors.lastname: Roussa
authors.forename: G J
authors.initials: GJ
authors.lastname: Cooper
authors.forename: C P
authors.initials: CP
authors.lastname: Smith
authors.forename: F
authors.initials: F
authors.lastname: Thévenod
authors.forename: M C
authors.initials: MC
authors.lastname: Steward
authors.forename: R M
authors.initials: RM
authors.lastname: Case
mesh_terms: D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / Q000494:pharmacology; D000328:Adult; D000368:Aged; D000584:Amiloride / Q000494:pharmacology; D000643:Ammonium Chloride / Q000494:pharmacology; D000818:Animals; D002462:Cell Membrane / Q000378:metabolism; D003001:Cloning, Molecular; D003592:Cytophotometry; D004232:Diuretics / Q000494:pharmacology; D005260:Female; D015870:Gene Expression; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007150:Immunohistochemistry; D008297:Male; D008564:Membrane Potentials / Q000502:physiology; D008839:Microelectrodes; D008875:Middle Aged; D009865:Oocytes / Q000378:metabolism; D010306:Parotid Gland / Q000166:cytology / Q000378:metabolism*; D020033:Protein Isoforms / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D012964:Sodium / Q000378:metabolism / Q000494:pharmacology; D027982:Sodium-Bicarbonate Symporters / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism; D017923:Sodium-Hydrogen Exchangers / Q000037:antagonists & inhibitors / Q000378:metabolism; D013223:Statistics as Topic; D014982:Xenopus laevis
chemical_list: D004232:Diuretics; D020033:Protein Isoforms; C498898:SLC4A4 protein, human; D027982:Sodium-Bicarbonate Symporters; D017923:Sodium-Hydrogen Exchangers; D000643:Ammonium Chloride; D000584:Amiloride; D012964:Sodium; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid