Gastric Antigen Challenge Releases Gastrin and Eicosanoids and Protects against Ethanol

Various gastrointestinal functions such as mucosal blood flow and mucus secretion can be influenced immunologically. Rats were systemically sensitized with 4-hydroxy-3-iodo-5-nitro-phenylacetic acid (NIP), a synthetic antigen. Mucosal release of gastrin, prostaglandin F2α, 6-keto-prostaglandin F1α, and leukotriene C4was measured after intragastric orin vitroantigen challenge. Gastric protection from ethanol was determined. In sensitized rats, intragastric antigen challenge increased release of gastrin from the antral mucosaex vivoand tended to increase release of prostaglandin F2α. Likewise, antral mucosa of sensitized rats released significantly more gastrin and prostaglandin F2αduringin vitroantigen challenge than during incubation in the absence of antigen. Release of 6-keto-prostaglandin F1αand leukotriene C4was not affected by the immunologic reaction. Topical antigen challenge in sensitized rats reduced gastric mucosal damage caused by ethanol by 50%. The immunologically induced gastroprotection was significantly attenuated by pretreatment with indomethacin. The findings show that specific antigen challenge renders the gastric mucosa more resistant against the injurious effect of ethanol indicating that the stomach is a target organ of immunological reactions. As gastrin and prostaglandins exert potent protective effects, release of these mediators may contribute to the protective response to gastric mucosal immune activation.