title: Targeted disruption of the Nhe1 gene prevents muscarinic agonist-induced up-regulation of Na(+)/H(+) exchange in mouse parotid acinar cells.
abstract: The onset of salivary gland fluid secretion in response to muscarinic stimulation is accompanied by up-regulation of Na(+)/H(+) exchanger (NHE) activity. Although multiple NHE isoforms (NHE1, NHE2, and NHE3) have been identified in salivary glands, little is known about their specific function(s) in resting and secreting acinar cells. Mice with targeted disruptions of the Nhe1, Nhe2, and Nhe3 genes were used to investigate the contribution of these proteins to the stimulation-induced up-regulation of NHE activity in mouse parotid acinar cells. The lack of NHE1, but not NHE2 or NHE3, prevented intracellular pH recovery from an acid load in resting acinar cells, in acini stimulated to secrete with the muscarinic agonist carbachol, and in acini shrunken by hypertonic addition of sucrose. In HCO(3)(-)-containing solution, the rate of intracellular pH recovery from a muscarinic agonist-stimulated acid load was significantly inhibited in acinar cells from mice lacking NHE1, but not in cells from NHE2- or NHE3-deficient mice. These data demonstrate that NHE1 is the major regulator of intracellular pH in both resting and muscarinic agonist-stimulated acinar cells and suggest that up-regulation of NHE1 activity has an important role in modulating saliva production in vivo.
authors.affiliation: Center for Oral Biology, Rochester Institute of Biomedical Sciences, University of Rochester Medical Center, Rochester, New York 14642, USA.
authors.forename: R L
authors.initials: RL
authors.lastname: Evans
authors.forename: S M
authors.initials: SM
authors.lastname: Bell
authors.forename: P J
authors.initials: PJ
authors.lastname: Schultheis
authors.forename: G E
authors.initials: GE
authors.lastname: Shull
authors.forename: J E
authors.initials: JE
authors.lastname: Melvin
mesh_terms: D000643:Ammonium Chloride / Q000494:pharmacology; D000818:Animals; D001639:Bicarbonates / Q000378:metabolism; D005260:Female; D005452:Fluoresceins; D005456:Fluorescent Dyes; D018390:Gene Targeting; D006863:Hydrogen-Ion Concentration; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D008856:Microscopy, Fluorescence; D018721:Muscarinic Agonists / Q000494:pharmacology*; D010306:Parotid Gland / Q000187:drug effects / Q000378:metabolism*; D012463:Saliva / Q000378:metabolism; D000074083:Sodium-Hydrogen Exchanger 3; D017923:Sodium-Hydrogen Exchangers / Q000235:genetics* / Q000378:metabolism; D015854:Up-Regulation / Q000187:drug effects
chemical_list: D001639:Bicarbonates; D005452:Fluoresceins; D005456:Fluorescent Dyes; D018721:Muscarinic Agonists; C513111:Slc9a2 protein, mouse; C000613386:Slc9a3 protein, mouse; D000074083:Sodium-Hydrogen Exchanger 3; D017923:Sodium-Hydrogen Exchangers; C069139:growth factor-activatable Na-H exchanger NHE-1; D000643:Ammonium Chloride; C057433:2',7'-bis-(2-carboxyethyl)-5(6)-carboxyfluorescein acetoxymethyl ester