Pancreatic, Hepatic, and Duodenal Mucosal Bicarbonate Secretion during Infusion of Secretin and Cholecystokinin: Evidence of the Importance of Hepatic Bicarbonate in the Neutralization of Acid in the Duodenum of Anaesthetized Pigs

Abstract

The effect of infusion of secretin alone or in combination with cholecystokinin (CCK) on pancreatic, hepatic, and duodenal mucosal bicarbonate secretion was studied in anaesthetized pigs. After laparotomy, catheters were inserted into the common bile duct, the pancreatic duct, and both ends of the duodenum. Pancreatic, hepatic, and duodenal mucosal secretions were collected during intraportal infusion of increasing doses of secretin, either alone or in combination with CCK. During infusion of secretin in doses that caused physiologic increases in plasma secretin concentrations the liver produced significantly more bicarbonate than the pancreas. A physiologic dose of CCK augmented the effect of secretin on both hepatic and pancreatic bicarbonate secretion, but the hepatic production of bicarbonate was still larger than the pancreatic production. Neither secretin alone nor secretin combined with CCK caused any changes in duodenal mucosal bicarbonate secretion. These results suggest that the liver plays an important role in the neutralization of acid in the duodenum.

Regulation of Pancreatic Secretion

“…27 Maximum bicarbonate concentration in humans may be as high as 150 mM, which is approximately twice as great as that in the rat. Sampling from the duodenum is fraught with hazards.…”

The Cystic Fibrosis of Exocrine Pancreas

“…As discussed in a review (Heitzmann and Warth 2007), it seems that the effect of CFTR on acid secretion may depend on the particular CFTR mutation and rescue by other Cl 2 transporters/channels. Normally, acid chyme is neutralized by HCO 3 2 secreted by duodenal epithelia, pancreatic duct and bile duct secretions (Ainsworth et al 1991). Therefore, duodenal hyperacidity in CF has been ascribed to loss-of-function in the CFTR transporter, especially in duodenal and pancreatic epithelia.…”

Relative Importance of Pancreatic, Hepatic, and Mucosal Bicarbonate in Duodenal Neutralization of Acid in Anaesthetized Pigs

“…This, again, is supported by the fact that both hepatic and duodenal mucosal secretion of bicarbonate is stimulated by duodenal acidification (6,13) or by intravenous infusion of secretin or vasoactive intestinal peptide (VIP) (14)(15)(16), both of which are normally released to the blood stream by duodenal acidification. Furthermore, recent studies in our laboratory have shown that the secretion of bicarbonate from the porcine liver is greater than the secretion of bicarbonate from the pancreas during infusion of physiologic doses of secretin alone or in combination with cholecystokinin (CCK) (17). The purpose of the present study was to determine the relative importance of bicarbonate secretion from the liver, pancreas, and duodenal mucosa in neutralizing acid within the duodenal lumen.…”