Document Detail

Gastroduodenal mucus bicarbonate barrier: protection against acid and pepsin.
MedLine Citation:
PMID:  15591243     Owner:  NLM     Status:  MEDLINE    
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 digestion. In this article we review the present state of the gastroduodenal mucus bicarbonate barrier two decades after the first supporting experimental evidence appeared. The primary function of the adherent mucus gel layer is a structural one to create a stable, unstirred layer to support surface neutralization of acid and act as a protective physical barrier against luminal pepsin. Therefore, the emphasis on mucus in this review is on the form and role of the adherent mucus gel layer. The primary function of the mucosal bicarbonate secretion is to neutralize acid diffusing into the mucus gel layer and to be quantitatively sufficient to maintain a near-neutral pH at the mucus-mucosal surface interface. The emphasis on mucosal bicarbonate in this review is on the mechanisms and control of its secretion and the establishment of a surface pH gradient. Evidence suggests that under normal physiological conditions, the mucus bicarbonate barrier is sufficient for protection of the gastric mucosa against acid and pepsin and is even more so for the duodenum.
Adrian Allen; Gunnar Flemström
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't; Review    
Journal Detail:
Title:  American journal of physiology. Cell physiology     Volume:  288     ISSN:  0363-6143     ISO Abbreviation:  Am. J. Physiol., Cell Physiol.     Publication Date:  2005 Jan 
Date Detail:
Created Date:  2004-12-13     Completed Date:  2005-03-07     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  100901225     Medline TA:  Am J Physiol Cell Physiol     Country:  United States    
Other Details:
Languages:  eng     Pagination:  C1-19     Citation Subset:  IM    
Physiological Sciences, Medical School, University of Newcastle upon Tyne, Newcastle upon Tyne, United Kingdom.
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MeSH Terms
Bicarbonates / metabolism*
Duodenum / physiology
Gastric Acid / metabolism*
Gastric Mucosa / physiology*
Intestinal Mucosa / physiology*
Pepsin A / metabolism*
Reg. No./Substance:
0/Bicarbonates; EC A

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