Serosal bicarbonate protects against acid injury to rabbit esophagus.
The role of serosal bicarbonate ions (HCO3-) in protection against acid injury was investigated in rabbit esophageal mucosa mounted in Ussing chambers. Luminal acidification reduced potential difference and resistance in tissues exposed serosally to HCO3- or (unbuffered) HCO3-free solution. Whereas resistance declined similarly in both groups, potential difference declined less in HCO3- solution. After washout, HCO3-bathed tissues also had a greater increase in resistance, lower permeability to mannitol, and less histologic damage. Furthermore, as protection by HCO3- was not blocked by pretreatment with either the anion exchange blocker, 4 acetamido-4'-isothiocyanatostilbene 2-2'-disulfonic acid, or the carbonic anhydrase inhibitor, acetazolamide, and replacement of HCO3- with N-2-hydroxyethylpiperazine-N'-2-ethane sulfonic acid, a buffer impermeant to cells, was protective, an extracellular site for protection by HCO3- was likely. Where in the extracellular space HCO3- buffers H+ is unclear, but the absence of change in luminal pH and the inability to prevent the acid-induced increase in permeability in HCO3-bathed tissues argue against a luminal (preepithelial) site. Also, rapid repair was not demonstrated, indicating that a luminal site for protection after surface cell damage was unlikely. We conclude that serosal HCO3- is important in esophageal protection against acid damage by buffering H+ within the intercellular compartment of the extracellular space.
Tobey
N A
NA
Department of Medicine, University of North Carolina School of Medicine, Chapel Hill.
Powell
D W
DW
Schreiner
V J
VJ
Orlando
R C
RC
D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid / Q000494:pharmacology; D000086:Acetazolamide / Q000494:pharmacology; D000818:Animals; D001639:Bicarbonates / Q000502:physiology*; D004947:Esophagus / Q000502:physiology*; D005753:Gastric Mucosa / Q000502:physiology*; D005764:Gastroesophageal Reflux / Q000503:physiopathology*; D006531:HEPES / Q000494:pharmacology; D006851:Hydrochloric Acid / Q000494:pharmacology; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000187:drug effects; D011817:Rabbits
D001639:Bicarbonates; D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid; D000086:Acetazolamide; D006851:Hydrochloric Acid; D006531:HEPES