INTRACELLULAR PH IN RAT PANCREATIC DUCTS

In order to study the mechanism of H+ and HCO3- transport in a HCO3- s ecreting epithelium, pancreatic ducts, we have measured the intracellu lar pH (pH(i)) in this tissue using the pH sensitive probe BCECF. We f ound that exposures of ducts to solutions containing acetate/acetic ac id or NH4+/NH3 buffers (20 mmol/1) led to pH(i) changes in accordance with entry of lipid-soluble forms of the buffers, followed by back-reg ulation of pH(i) by duct cells. In another type of experiment, changes in extracellular pH of solutions containing HEPES or HCO3-/CO2 buffer s led to significant changes in pH(i) that did not seem to be back-reg ulated efficiently by duct cells. The sensitivity of pH(i) to the inhi bitor HOE 694 and to changes in Na+ gradients, indicate that the Na+/H + exchanger is present in this epithelium. Similarly, the sensitivity to Cl- and HCO3- gradients indicated the presence of the Cl-/HCO3- exc hanger. Under some conditions, these exchangers can be invoked to regu late cell pH. (C) 1997 Elsevier Science Inc.