In situ micropuncture study of pancreatic duct pH.

The pH and chloride concentration in the extralobular duct system of the rabbit pancreas was investigated by using glass-membrane pH microelectrodes and microsampling techniques. The response of pH microelectrodes was compared to that of a pH macroelectrode system in buffer solutions containing common interfering substances and it was found that the electrodes were insensitive to these substances. Final pancreatic juice electrolyte concentrations and osmolality were found to be similar to that observed by others. Under free-flow conditions, a significant pH gradient was found between small extralobular ducts (7.47) and final juice (8.03). This gradient was nearly obliterated on stimulation with secretin. Duct chloride concentrations were found to be similar in all duct sizes and final juice under unstimulated conditions and after stimulation with secretin. It is concluded that glass-membrane pH microelectrodes are reliable and accurate indicators of pH in this system. The present experiments suggest that the entire extralobular ductal system may participate in the secretion of an alkaline fluid.