title: The importance of mucus layers and bicarbonate transport in preservation of gastric juxtamucosal pH.
abstract: Mucus thickness is suggested to be related to mucosal protection. We therefore investigated the importance of the removable mucous layer and epithelial bicarbonate transport in preservation of the gastric juxtamucosal pH (pH(jm)) during luminal acid. Anesthetized rats were prepared for intravital microscopy of the gastric mucosa, and pH(jm) was measured with pH-sensitive microelectrodes. The mucus was either left intact (IM) or removed (MR) down to the firmly attached mucous layer, and HCl (pH 1) was applied luminally. Removal of the loosely adherent mucous layer did not influence the pH(jm) during luminal acid (pentagastrin: IM/MR 7.03 +/- 0.09/6.82 +/- 0.19; pentagastrin + indomethacin: IM/MR 6.89 +/- 0.20/6.95 +/- 0.27; ranitidine: IM/MR 2.38 +/- 0.64/2.97 +/- 0.62), unless prostaglandin synthesis and acid secretion were inhibited (ranitidine + indomethacin: IM/MR 2.03 +/- 0.37/1.66 +/- 0.18). Neutral pH(jm) is maintained during endogenous acid secretion and luminal pH 1, unless DIDS was applied luminally, which resulted in a substantially decreased pH(jm) (1.37 +/- 0.21). Neutral pH(jm) is maintained by a DIDS-sensitive bicarbonate transport over the surface epithelium. The loosely adherent mucous layer only contributes to maintaining pH(jm) during luminal pH 1 if acid secretion and prostaglandin synthesis are inhibited.
authors.affiliation: Division of Physiology, Department of Medical Cell Biology, University of Uppsala, 751 23 Uppsala, Sweden. Mia.Phillipson@physiology.uu.se
authors.forename: Mia
authors.initials: M
authors.lastname: Phillipson
authors.forename: Christer
authors.initials: C
authors.lastname: Atuma
authors.forename: Johanna
authors.initials: J
authors.lastname: Henriksnäs
authors.forename: Lena
authors.initials: L
authors.lastname: Holm
mesh_terms: D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / Q000494:pharmacology; D000818:Animals; D000897:Anti-Ulcer Agents / Q000494:pharmacology; D001639:Bicarbonates / Q000378:metabolism*; D001692:Biological Transport / Q000187:drug effects / Q000502:physiology; D027963:Chloride-Bicarbonate Antiporters / Q000378:metabolism; D016861:Cyclooxygenase Inhibitors / Q000494:pharmacology; D005744:Gastric Acid / Q000378:metabolism*; D005753:Gastric Mucosa / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration / Q000187:drug effects*; D007213:Indomethacin / Q000494:pharmacology; D008297:Male; D010418:Pentagastrin / Q000494:pharmacology; D011899:Ranitidine / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D000897:Anti-Ulcer Agents; D001639:Bicarbonates; D027963:Chloride-Bicarbonate Antiporters; D016861:Cyclooxygenase Inhibitors; D011899:Ranitidine; D010418:Pentagastrin; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; D007213:Indomethacin