Effects of sodium salicylate and acetylsalicylic acid on intramural pH and ulceration of rabbit antral mucosa.

This study examines the relationship between the pH within the middle third of antral mucosa (intramural pH [IMpH]) and the development of ulceration caused by salicylates. Luminal soldium salicylate does not significantly alter the IMpH or cause ulceration of mucosa maintained at luminal pH 7. Salicylate at pH 3.5 initially decrease IMpH (7.28 to 6.75), during which time ulceration occurs. IMpH subsequently increase, resulting in profound alkalinization (pH 7.67) associated with increased HCO3 secretion. Salicylate at pH 1 causes a sustained decrease in IMpH (6.57), which is associated with more severe ulceration. Neither sodium salicylate nor acetylsalicylic acid given intravenously affects. IMpH or causes ulceration at luminal pH 7 or 3.5. However, at pH 1 both salicylate compounds cause ulceration and subtle changes in net ion fluxes without altering IMpH. The data suggest that acidification of the midportion of the mucosa in general is not a prerequisite for the occurrence of gross damage, and the damaging effects of intravenous salicylates cannot be explained by thier metabolic actions alone. However, it appears that the metabolic effects of salicylate make the mucosa more susceptible to the deleterious effects of diffusing acid. Since intravenous sodium salicylate and acetylsalicylic acid both cause ulceration but only acetylsalicylic acid alters prostaglandin synthesis, interference with prostaglandin metabolism does not appear to be a prerequisite for the occurrence of ulceration.