Human proximal duodenal alkaline secretion is mediated by Cl-/HCO3- exchange and HCO3- conductance
L Nyberg1, V Pratha, D L Hogan
1Division of Gastroenterology, UCSD Medical Center, University of California San Diego, 92103, USA.
Abstract:
The proximal duodenal epithelium secretes bicarbonate into an adherent mucus layer, thereby protecting the mucosa from injury by gastric acid and pepsin. While bicarbonate secretion is stimulated and inhibited by a number of agonists and antagonists, the apical anion transport pathways have not been addressed fully. The objective was to assess if apical Cl-/HCO3- exchange and Cl-:HCO3- conductance are involved in duodenal mucosal bicarbonate secretion (DMBS). In healthy volunteers, the proximal 4 cm of duodenum was isolated, perfused with either saline or 4,4'-diisothiocyano-2,2'-disulfonic acid (DIDS), and bicarbonate secretion and transepithelial potential difference (PD) were stimulated by either PGE2 or the phosphodiesterase inhibitor theophylline to increase cyclic AMP. Luminal DIDS abolished PGE2-stimulated DMBS, yet had no effect on the increase in PD and failed to significantly alter theophylline-induced DMBS and PD. Therefore, in human proximal duodenum, it appears that PGE2 and cAMP activate distinct HCO3- transport pathways likely involving a DIDS-sensitive Cl-/HCO3- exchanger and DIDS-insensitive HCO3- conductance.
Related Concept Videos
Stomach pH Regulation
The acid-secreting gastric mucosal epithelial cells (parietal cells) lining the stomach lumen maintain the low pH in the lumen. Numerous ion transporters and channels on these parietal...
pH Homeostasis
Respiratory Regulation of...
Mucosal Barrier of the Stomach
Within parietal cells, carbonic acid is first formed through the reaction of water and carbon dioxide. The dissociation of carbonic acid releases bicarbonate and hydrogen ions. The bicarbonate...
Pancreatic Juice and Secretion
When acidic chyme from the stomach enters the duodenum, it triggers the release of secretin, a hormone that prompts pancreatic juice secretion. After a fatty meal, cholecystokinin, another hormone, stimulates gallbladder contraction and enhances enzyme-rich...
Reabsorption and Secretion in the DCT and Collecting Duct
The distal part of the DCT, along with the...
Renal Regulation of Acid-Base Balance
In the kidneys, cells within the proximal convoluted tubules (PCT) and the collecting ducts secrete hydrogen ions (H+) into the tubular fluid. Specifically, in the PCT, Na+/H+ antiporters secrete H+ while reabsorbing Na+.
However, the intercalated cells in...


