[Protective action of endogenous opioid-like peptides of different origins in duodenal ulcer in rats].

A study was made of the effects of some endogenous opioids (beta-endorphin, gamma-endorphin, met-enkephalin, leu-enkephalin and dinorphin) formed in the body from different high-molecular precursors (pro-opiomelanocortin, proenkephalins A and B) on the development in rats of the cysteamine-induced duodenal ulcers. All the peptides under study, gamma-endorphin, in particular, had an anti-ulcerous activity which was mediated by specific opiate receptors. The majority of the opioids was characterized by reduction of the anti-ulcerous effect as the dose was raised. It is assumed that protection of the duodenal mucosa under ulcerogenic exposures is an essential property of endogenous peptides. It is concluded that opioid peptides derived from different precursors are arranged in a complex synergic system responsible for cytoprotection of the duodenum.