| Popis: |
The proximal duodenal epithelium secretesbicarbonate into an adherent mucus layer, therebyprotecting the mucosa from injury by gastric acid andpepsin. While bicarbonate secretion is stimulated andinhibited by a number of agonists and antagonists, theapical anion transport pathways have not been addressedfully. The objective was to assess if apicalCl-/HCO3- exchange andCl-:HCO3- conductanceare involved in duodenal mucosal bicarbonate secretion(DMBS). In healthy volunteers, the proximal 4 cm ofduodenum was isolated, perfused with either saline or4,4′-diisothiocyano-2,2′-disulfonic acid(DIDS), and bicarbonate secretion and transepithelial potentialdifference (PD) were stimulated by eitherPGE2 or the phosphodiesterase inhibitortheophylline to increase cyclic AMP. Luminal DIDSabolished PGE2-stimulated DMBS, yet had no effect on the increase in PD andfailed to significantly alter theophylline-induced DMBSand PD. Therefore, in human proximal duodenum, itappears that PGE2 and cAMP activate distinctHCO transport pathways 2 likely involving a DIDS-sensitiveCl-/HCO3- exchanger andDIDS-insensitive HCO3-conductance. |
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