Evidence for an anion exchanger in the mouse lacrimal gland acinar cell membrane |
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Authors: | Terutaka Ozawa Yoshitaka Saito Akinori Nishiyama |
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Institution: | (1) Department of Physiology, Tohoku University School of Medicine, 980 Sendai, Japan |
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Abstract: | Summary 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 HCO
3
–
-free solution of pH 7.4 (HEPES/Tris buffered), pHi was 7.25 andaCli was 33mm. By an exposure to a HCO
3
–
(25mm HCO
3
–
/5% CO2, pH 7.4) solution for 15 min,aCli was decreased to 25mm and pHi was transiently decreased to about 7.05 within 1 min, then slowly relaxed to 7.18 in 15 min. Intracellular HCO
3
–
concentration HCO
3
–
]i, calculated by the Henderson-Hasselbalch's equation, was 11mm at 1 min after the exposure and then slowly increased to 15mm. Readmission of the HCO
3
–
-free solution reversed the changes inaCli and pHi. The intracellular buffering power was about 40mm/pH. An addition of DIDS (0.2mm) significantly inhibited the rates of change inaCli, pHi, and HCO
3
–
]i caused by admission/withdrawal of the HCO
3
–
, solution and decreased the buffer value. Replacement of all Cl– with gluconate in the HCO
3
–
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 (0.3mm). In the HCO
3
–
solution, a stimulation of intracellular HCO
3
–
production by exposing the tissue to 25mm NH
4
+
increasedaCli significantly. While in the HCO
3
–
-free solution or in the HCO
3
–
, solution containing DIDS, exposure to NH
4
+
had little effect onaCli. All of these findings were consistent with the presence of a reversible, disulfonic stilbene-sensitive Cl–/HCO
3
–
exchanger in the basolateral membrane of the acinar cells. The possibility of anion antiport different from one-for-one Cl–/HCO
3
–
exchange is discussed. |
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Keywords: | lacrimal gland intracellular pH intracellular Cl– Cl– /HCO
3
– exchange DIDS membrane transport |
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