Evidence for an anion exchanger in the mouse lacrimal gland acinar cell membrane.
Anion exchange transport in the mouse lacrimal gland acinar cell membrane was studied by measuring the intracellular H+ (pHi) and Cl- (aCli) activities with double-barreled ion-selective microelectrodes. In a HCO3- -free solution of pH 7.4 (HEPES/Tris buffered), pHi was 7.25 and aCli was 33 mM. By an exposure to a HCO3- (25 mM HCO3-/5% CO2, pH 7.4) solution for 15 min, aCli was decreased to 25 mM, and pHi was transiently decreased to about 7.05 within 1 min, then slowly relaxed to 7.18 in 15 min. Intracellular HCO3- concentration [HCO3-]i, calculated by the Henderson-Hasselbalch's equation, was 11 mM at 1 min after the exposure and then slowly increased to 15 mM. Readmission of the HCO3(-)-free solution reversed the changes in aCli and pHi. The intracellular buffering power was about 40 mM/pH. An addition of DIDS (0.2 mM) significantly inhibited the rates of change in aCli, pHi, and [HCO3-]i caused by admission/withdrawal of the HCO3- solution and decreased the buffer value. Replacement of all Cl- with gluconate in the HCO3- solution increased pHi, and readmission of Cl- decreased pHi. The rates of these changes in pHi were reduced by DIDS by 32-45% but not by amiloride (0.3 mM). In the HCO3- solution, a stimulation of intracellular HCO3- production by exposing the tissue to 25 mM NH4+ increased aCli significantly. While in the HCO3(-)-free solution or in the HCO3- solution containing DIDS, exposure to NH4+ had little effect on aCli.(ABSTRACT TRUNCATED AT 250 WORDS)
Ozawa
T
T
Department of Physiology, Tohoku University School of Medicine, Sendai, Japan.
Saito
Y
Y
Nishiyama
A
A
D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D000641:Ammonia / Q000494:pharmacology; D000818:Animals; D000837:Anion Exchange Resins / Q000032:analysis*; D017920:Antiporters; D001639:Bicarbonates / Q000032:analysis; D002352:Carrier Proteins / Q000032:analysis; D002462:Cell Membrane / Q000032:analysis / Q000502:physiology / Q000648:ultrastructure; D002712:Chlorides / Q000032:analysis / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007475:Ion Exchange Resins / Q000032:analysis*; D007765:Lacrimal Apparatus / Q000032:analysis* / Q000502:physiology / Q000648:ultrastructure; D051379:Mice
D000837:Anion Exchange Resins; D017920:Antiporters; D001639:Bicarbonates; D002352:Carrier Proteins; D002712:Chlorides; D007475:Ion Exchange Resins; D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid; D000641:Ammonia; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid