CHLORIDE-BICARBONATE EXCHANGE IN ISOLATED RAT PANCREATIC ACINI

¹ Department of Physiological Sciences, University Medical School, Framlington Place, Newcastle upon Tyne NE2 4HH

We have measured the intracellular pH (pH_i) of single isolated rat pancreatic acini using the fluorescent dye dicyano-hydroquinone (DCH). Steady-state pH_i was unaffected by either acetylcholine (10, µM), caerulein (10 nM) or secretin (1 nM), or by the anion exchange inhibitor DIDS (1 mM) and only changed by 0·32 units when extracellular pH was varied over the range from 6·8 to 8·4. However, replacing extracellular chloride with gluconate, such that the final bath chloride concentration was less than 20 mm, caused a marked alkalinization of pH_i to a new steady-state value. The rate of pH_i alkalinization under these conditions was bicarbonate- dependent, blocked by pre-incubation of the acini with 1 mM-DIDS, but unaffected by removal of extracellular sodium. These observations are consistent with the presence of a Cl^--HCO₃^- exchanger on rat pancreatic acinar cells. Since DIDS had no effect on steady-state pH_i the anion exchanger is unlikely to play a role in pH_i regulation. However, rat pancreatic acini secrete a NaCl-rich fluid and the Cl^--HCO₃^- exchanger might function in parallel with Na⁺-H⁺ exchangers to provide a mechanism for chloride accumulation across the basolateral membrane of the acinar cells.

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