AJP - Gastrointestinal and Liver Physiology, Vol 246, Issue 2 114-G119, Copyright © 1984 by American Physiological Society
Backdiffusion of H+ in isolated frog gastric mucosa
R. P. Durbin
Backdiffusion of H+ was studied in isolated bullfrog gastric mucosa using
direct titration to evaluate changes in luminal H+ level. In resting
mucosae, the resulting permeability coefficient for H+ (uncorrected for
electrical effects) was 0.4 X 10(-5) cm X S-1, which is of the same order
of magnitude as that estimated from data in the literature for dog and
rabbit gastric mucosa in vivo. With maximal stimulation of acid secretion,
backdiffusion of H+ was considerably increased. In both resting and
stimulated mucosae, an increase in Cl- flux from lumen to serosa was
observed to accompany H+ backdiffusion. In experiments in which electrical
activity of resting mucosae was monitored, instilled H+ lowered gastric
potential difference but had little effect on the normal resistance. Sudden
drops in resistance and potential were observed, independent of luminal
acid; after such events instilled H+ had no effect on mucosal resistance.
It appears that a substantial part of H+ backdiffusion occurs as the ion
pair HCl.
