AJP - Gastrointestinal and Liver Physiology, Vol 268, Issue 2 200-G206, Copyright © 1995 by American Physiological Society
Luminal dilution caused by certain mild irritants and capsaicin contributes to their gastric mucosal protection
Y. Hatakeyama, M. Matsuo, M. Tomoi, M. Ohtsuka and K. Shimomura
Department of Pharmacology, Fujisawa Pharmaceutical, Osaka, Japan.
We have recently shown that certain mild irritants caused the increase in
fluid volume in the rat stomach. The present study was conducted to
investigate 1) whether standing fluid in the gastric cavity can prevent
gastric mucosal injury caused by 0.6 N HCl and 2) the mechanisms by which
certain mild irritants increase the gastric fluid volume. One milliliter of
water administered immediately before irritants greatly inhibited gastric
lesion formation. Sodium chloride and capsaicin induced a profound
enhancement of gastric fluid volume, as acid mild irritants did also.
Sensory denervation completely abolished the volume increase caused by
capsaicin but hardly influenced that caused by mild irritants. Capsaicin
increased the amount of Evans blue in the gastric fluid, but mild irritants
did not. On the other hand, HCl and capsaicin significantly inhibited the
emptying of phenol red. From these results, we conclude that mild irritants
and capsaicin can induce volume increase that by itself is enough to afford
protection through luminal dilution. Capsaicin but not mild irritants
requires sensory neurons to increase the gastric fluid volume. Certain mild
irritants may provide a fluid pooling effect partly by inhibiting gastric
emptying.
