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The barrier that protects the undamaged gastroduodenal mucosa from autodigestion by gastric juice is a dynamic multicomponent system. The major elements of this barrier are the adherent mucus gel layer, which is percolated by the HCO3- secretion from the underlying epithelial cells; the epithelial layer itself, which provides a permeability barrier and can(More)
Secretion of bicarbonate into the adherent layer of mucus gel creates a pH gradient with a near-neutral pH at the epithelial surfaces in stomach and duodenum, providing the first line of mucosal protection against luminal acid. The continuous adherent mucus layer is also a barrier to luminal pepsin, thereby protecting the underlying mucosa from proteolytic(More)
BACKGROUND/AIMS The gastric mucosa is covered by a continuous layer of bicarbonate-containing mucus gel; the question arises how acid, formed in the gastric glands, moves into the lumen. METHODS The pH in the gastric mucus gel and gel thickness were measured in anesthetized rats with pH-sensitive microelectrodes (tip diameter, 1-5 microns). RESULTS(More)
The gastroduodenal mucosa is a dynamic barrier restricting entry of gastric acid and other potentially hostile luminal contents. Mucosal HCO3(-) is a key element in preventing epithelial damage, and knowledge about HCO3(-) transport processes, including the role of the cystic fibrosis transmembrane conductance regulator channel, and their neurohumoral(More)
Luminal acid (10 mM HCl) is a stimulant of surface epithelial HCO-3 transport in mammalian stomach and duodenum in vivo. To determine whether a humoral mechanism is involved in mediation of this response, amphibian fundic, antral, or proximal duodenal mucosae were mounted in parallel in an in vitro chamber with their nutrient (serosal) surfaces facing a(More)
The relationship between surface epithelial alkaline secretion and pH at the mucosal cell surface was studied in the duodenum of anesthetized rats. Alkaline secretion was measured by direct titration in situ using perfused segments of duodenum just distal to the Brunner gland area and devoid of pancreatic and biliary HCO3-. Mucosal surface pH was measured(More)
Duodenal surface epithelial transport of HCO3(-) was measured by direct titration in anesthetized animals. Alkalinization of the lumen occurred in all species, although basal rates varied considerably: rats (approximately 10), cats (approximately 15), pigs (approximately 25), dogs (approximately 25), guinea pigs (approximately 40), and rabbits(More)
Gastric fundic mucosae in vitro from four species of frog and Necturus secrete HCO-3 at a steady-state rate of 0.25-0.55 microneq-cm-2-h-1 which corresponds to 5-10% of maximal H+ secretion. Net alkalinization was quantitated in mucosae with spontaneously resting H+ secretion or in mucosae inhibited by histamine H2-receptor antagonists or SNC-. HCO-3(More)
Effects of subulcerogenic doses of cysteamine (100 mg/kg s.c.) and propionitrile (5 mg/kg) on alkaline secretion by duodenal surface epithelium and pH at the surface of this mucosa were assessed in duodenum of anesthetized rats. Alkaline secretion was titrated in situ, using segments of duodenum just distal to the Brunner's glands area and devoid of(More)