SIMULTANEOUS MEASUREMENTS OF DUODENAL MUC OSAL AND BILIOPANCREATIC BICARBONATE SECRETION IN THE RAT

Objectives. - The aim of the present study was to assess the relative contribution of duodenal and biliopancreatic bicarbonate secretion to acid neutralization in the duodenum, in basal conditions, during stimu lation by PGE(2) and during acid infusion in the duodenum. Methods. - Forty rats were anaesthetized and the duodenum was infused with 0.9 % saline. Bicarbonate originating from duodenal mucosa and from biliopan creatic secretion was independently collected and measured. In neutral ization studies, HCl was infused in the duodenum, and the amount of re sidual acid escaping from the duodenum was determined with and without bile and/or pancreatic juice diversion. Results. - Basal duodenal and biliopancreatic bicarbonate outputs were respectively 10.0 +/- 0.66 a nd 2.4 +/- 0.31 mu mol/10 min. PGE(2) increased duodenal mucosal bicar bonate by about 100 %. Eighty-five pet-cent of infused HCl was neu neu tralized by duodenal mucosal bicarbonate. In neutralizing the remainin g 15 %, pancreatic secretion was slightly predominant, 46 % for a HCl concentration of 5 mM and 71 % for a NCl concentration of 40 mM. Concl usions. - These results shows that in the anaesthetized ed rat, availa ble bicarbonate in the duodenal lumen and HCl neutralization ability a re mainly dependent upon bicarbonate secreted by the duodenal mucosa.