Mechanisms involved in gastric mucosal resistance to injury.

The healthy stomach resists the potentially devastating effects of its own secreted H+. Even though the resulting concentration gradient favors diffusion of luminal H+ into the mucosa, the actual amount of diffusion is limited in extent under normal conditions. Enhanced diffusion of H+ into the mucosa can be associated with the development of obvious injury, but this is not necessarily the case if the tissue effectively buffers H+. Conversely, in circumstances where the ability to dispose of H+ is impaired, what would be considered to be a usual amount of H+ diffusion can be troublesome. While several factors of mucosal defense have been identified, it is unlikely that alteration of a single mechanism accounts for gross damage. The interplay between defensive mechanisms may account for the variable endoscopic effects observed for damaging agents in man, especially in situations where the luminal concentrations of H+ and drug are variable.