AJP - Gastrointestinal and Liver Physiology, Vol 248, Issue 5 587-G593, Copyright © 1985 by American Physiological Society
Characteristics of sudden potential drop in bullfrog gastric mucosa
J. B. Matthews, P. K. Rangachari, P. H. Rowe, R. Lange, G. Marrone and W. Silen
An unusual sudden potential drop (SPD) has been described by Kidder in
bullfrog gastric mucosa exposed to anoxia and a serosal pH less than or
equal to 7.1. We found that anoxia was not a prerequisite, since under
fully oxygenated conditions the SPD occurred reliably in metiamide-treated
tissues when the pH of the nutrient solution (pHN) was below 7.1. The SPD
was observed also in metiamide-treated tissues exposed to 20 mM luminal or
nutrient acetylsalicylic acid (ASA) with pHN = 7.3, an effect that was
abolished by increased nutrient HCO3- concentration. The SPD occurred when
NO3- but not isethionate or acetate replaced Cl- in the bathing media. A
marked increase in potential difference in response to changing luminal Cl-
concentration was observed after the SPD, uptake of Cl- from the luminal
solution into the tissue increased, but transmural fluxes of Cl- decreased
bidirectionally. Permeability to H+ was unaltered in the post-SPD state. An
SPD never occurred in antrum under conditions causing SPD in fundus,
suggesting that oxyntic cells are prerequisite. We conclude that, under
conditions which cause tissue or cellular acidosis and cessation of H+
secretion, fundic mucosae respond with an anion-selective increase in
apical permeability manifest as the SPD.
