Background. Our presentation comprises results of two studies: The first was an experimental investigation of 60 Wistar-strain rats used in a toxicological study. The other part analysed stress changes in the duodenal mucosa in the human autopsy material. Both humans and rats had been exposed to stress and showed similar histological changes. Methods and Results. In the rats the same duodenal lesions were present both in the test group and the control animals in the toxicological study. Lesions consisted of oedema of the duodenal villi and erosions in the tips of the villi.We believe that in the experimental group the stress was caused by restraining the animals by daily introduction of the gastric metallic tube, by taking blood from the retrobulbar plexus, and by anesthaesia. Conclusions. The autopsy study comprised 35 cases displaying congestion and macroscopicaly recognizable multifocal bleeding into the duodenal mucosal folds. The microscopic investigation revealed bleeding into the mucosal villi and small erosions. In some cases there were cuneiform mucosal infarcts extending into the submucosa. In the humans, severe cardiovascular diseases and circulatory disturbances represented the main causes of the stress. Local hypoxia and gastric juice acidity were invoved in the pathogenesis of the duodenal mucosal changes.

        Key words: stress, laboratory rats, autopsy, comparative pathology, duodenal mucosis, erosive duodenitis, ischemic changes, alarm reaction.