title: pH-sensitive anion exchanger in rat lacrimal acinar cells.
abstract: Basolateral membranes from rat lacrimal acinar cells contain Na(+)-H+ and Cl(-)-HCO3- antiport activities [Invest. Ophthalmol. Visual Sci. 28: 1726-1729, 1989; Am. J. Physiol. 255 (Gastrointest. Liver Physiol. 18): G367-G373, 1988]. This study evaluated factors involved in coupling ion fluxes through these antiporters. 22Na+ flux into acini isolated from rat exorbital glands was 94 +/- 6 nmol.mg-1.min-1, and it was accelerated threefold by 10(-5) M carbachol; neither resting nor stimulated influx was affected by bumetanide. It is, therefore, likely that a portion of the carbachol-dependent Na+ influx is mediated by Na(+)-H+ antiporters. 36Cl- flux into Cl(-)-loaded, unstimulated acini was 275 +/- 21 nmol.mg-1.min-1; Cl- flux into HCO3(-)-loaded acini was 204 +/- 2; Cl- flux into acini loaded with both Cl- and HCO3- was 253 +/- 32; and influx in the absence of exchangeable intracellular anions was 176 +/- 13. Therefore, Cl(-)-Cl- self-exchange represented the major component of anion exchanger-mediated Cl- flux into resting cells. As pHi was increased above 7.2 by potassium-nigericin pH clamping, Cl- fluxes into Cl(-)- and HCO3(-)-containing acini, but not into Cl(-)-depleted acini, were significantly accelerated. SITS completely abolished the pHi-activated increment of Cl(-)-Cl- exchange. Carbachol increased Cl- unidirectional flux into Cl(-)-loaded cells by 25% (P less than 0.1), apparently as a result of Na(+)-H+ antiporter-mediated cytoplasmic alkalinization.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Physiology and Biophysics, University of Southern California School of Medicine, Los Angeles 90033.
authors.forename: R W
authors.initials: RW
authors.lastname: Lambert
authors.forename: M E
authors.initials: ME
authors.lastname: Bradley
authors.forename: A K
authors.initials: AK
authors.lastname: Mircheff
mesh_terms: D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid / Q000494:pharmacology; D000818:Animals; D001639:Bicarbonates / Q000378:metabolism*; D002217:Carbachol / Q000494:pharmacology; D002352:Carrier Proteins / Q000378:metabolism*; D027963:Chloride-Bicarbonate Antiporters; D002712:Chlorides / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D007700:Kinetics; D007765:Lacrimal Apparatus / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D008297:Male; D008954:Models, Biological; D051381:Rats; D011919:Rats, Inbred Strains; D012964:Sodium / Q000378:metabolism*
chemical_list: D001639:Bicarbonates; D002352:Carrier Proteins; D027963:Chloride-Bicarbonate Antiporters; D002712:Chlorides; D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid; D002217:Carbachol; D012964:Sodium