In 'defence' of the gastric mucosa.

For many years physiological properties within the body that lead to or prevent ulceration of gastric and duodenal mucosa have been thought of as being 'aggressive' or 'defensive' in nature. Peptic ulcer has been assumed to develop when the summation of aggressive factors is greater than defensive, and a past concept has assumed that an increase in the latter or decrease in the former would lead to a decreased propensity of the mucosa to ulcerate. The reasons for the resistance of normal gastric mucosa to self-digestion have long been sought. It is known that exposure of intestinal mucosa to gastric juice can induce the formation of ulcerations" 1a. Possibly back diffusion of acid into gastric mucosa can do the same. Are there any specific properties of the gastric mucosa that might contribute to a defence against ulceration, and, in particular, might it be possible to enhance any of these properties? A number of factors that are believed to act to defend the mucosa have been observed in the past. For example, well known physiological mechanisms that inhibit excessive gastric secretion in response to the presence of gastric juice in gastric antrum or duodenum have been observed2' 3. A variety of experiments have also suggested that nutritional factors and normal intake of dietary protein4 5 as well as growth hormone6 help to maintain this resistance of the mucosal cells against ulceration. Of particular interest for many years has been the postulated 'first line of defence' against mucosal injury, the mucus layer provided by the epithelial cells of the stomach7. This layer of mucus, together with the 'second line of defence', the healthy epithelial cells themselves, have been thought to play a significant role in defence of the mucosa against injury and ulceration. The mucus-producing epithelial cells lining the gastric pits and surface of the mucosa are believed to supply mucus quite rapidly to produce a coat protecting the cells against injury. In recent years additional elements that relate to the production of mucus and the epithelial cells themselves (the 'first' and 'second' lines of defence) have been developed. New information about how these cells are produced, and how they develop and mature in the gastric mucosa has emerged. This information is pertinent to an analysis of how the epithelial cells are able to remain viable in the gastric milieu. This information has indicated a dynamic and rapid life cycle of the …