Distinct effects of tetragastrin in rat gastroduodenal mucosa on mucin content and mucosal protective action against histamine-induced injury.

We examined the effects of tetragastrin on mucin (mucus glycoprotein) content and mucosal damage in the rat stomach and duodenum. Following an injection of tetragastrin (12, 120, or 400 microg/kg subcutaneously), no macroscopic damage was found to the gastric mucosa but an increase in corpus mucin content was noted, whereas mucosal lesions appeared and the mucin content decreased in the duodenum in a dose-related manner. In the groups with histamine (0.8, 8, or 80 mg/kg intraperitoneally) administration, the extent of mucosal damage and the decrease in mucin content were dose-related in both these regions. For assessment of the effect of tetragastrin on the protective action in gastroduodenal mucosa, changes in mucin content and mucosal damage with histamine (80 mg/kg) -induced injury were examined. Coadministration of tetragastrin prevented the gastric mucosal damage and inhibited the decrease in corpus mucin content. In the duodenum, tetragastrin aggravated the histamine-induced mucosal damage and did not inhibit the reduction of the mucin content. From the present results, the increase in gastric mucins induced by tetragastrin might be related to the protective effect of gastric mucosa against injury. Tetragastrin did not protect the duodenal mucosa, and histamine-induced injury occurring in this region would be aggravated by the increase in HCl secretion and the decrease in mucin content induced by tetragastrin.