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Gastrointestinal mucosal protective mechanisms: Mudolatory effects of Heliobacter pyroli on the gastric mucus gel barrier and mucosal blood flow in vivo
Uppsala University, Medicinska vetenskapsområdet, Faculty of Medicine, Department of Physiology.
2000 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The gastrointestinal mucus gel layer and blood flow are two important mechanisms for protection at the pre-epithelial and sub-epithelial levels, respectively. Helicobacter pylori might circumvent these mechanisms and elicit a chronic inflammatory response with consequent ulcers in the stomach and duodenum. In this thesis, the physical state and properties of the adherent mucus gel layer was studied from the stomach to colon. Furthermore, the acute and chronic effects of H. pylori on the integrity of the mucus gel layer and mucosal blood flow were studied in the anesthetized rat.

A translucent mucus gel covers all studied segments of the gastrointestinal tract during fasting conditions, with the thickest layers in the colon and ileum. Carefully applied suction revealed that the mucus gel was a multi-layered structure comprising a firmly adherent layer covering the mucosa, impossible to remove, and a loosely adherent upper layer. The firmly adherent layer was thick and continuous in the corpus (80μm), antrum (154μm) and colon (116μm), but thin (<20μm) and discontinuous in the small intestine.

Following mucus removal, a rapid renewal of the loosely adherent layer ensued. The highest rate was observed in the colon with intermediate values in the small intestine. Mucus renewal in the stomach was attenuated on acute luminal application of water extracts from H. pylori (HPE). In animals with a chronic H. pylori infection the mucus renewal rate was unaffected, but the total gastric mucus gel thickness was reduced and the mucus secretory response to luminal acid (pH1) attenuated in the antrum.

HPE from type I strains acutely reduced corporal mucosal blood flow, measured with laser-Doppler flowmetry, by approximately 15%. The reduction in blood flow was mediated by a heat stable factor other than VacA and CagA. Inhibition of endogenous nitric oxide production with Nω-nitro-l-arginine augmented the decrease. However, ketotifen, a mast cell stabilizer, completely attenuated the effect of the extract as did the platelet activating factor (PAF) receptor-antagonist, WEB2086, thus depicting a detrimental role for the microvascular actions of PAF.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis , 2000. , p. 60
Series
Comprehensive Summaries of Uppsala Dissertations from the Faculty of Medicine, ISSN 0282-7476 ; 972
Keywords [en]
Physiology and anatomy, mucus gel layer, mucosal blood flow, mucus thickness, chronic infection, rat, platelet activating factor, mast cell, nitric oxide, nitric oxide synthase, ketotifen, intra-vital microscopy, microelectrode, laser-Doppler flowmetry, L- NNA
Keywords [sv]
Fysiologi och anatomi
National Category
Physiology
Research subject
Physiology
Identifiers
URN: urn:nbn:se:uu:diva-1258ISBN: 91-554-4851-8 (print)OAI: oai:DiVA.org:uu-1258DiVA, id: diva2:160819
Public defence
2000-12-01, Sal B21, Biomedicinskt centrum (BMC), Uppsala, 09:15
Available from: 2000-11-10 Created: 2000-11-10 Last updated: 2018-01-13Bibliographically approved

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