Intestinal diamine oxidase and histamine release in rabbit mesenteric ischemia

It has been suggested that histamine contributes to lethal circulatory collapse after acute superior mesenteric artery occlusion. The activity of the histamine inactivating enzyme diamine oxidase, the release of the amine, and the effect of histamine receptor antagonists was therefore studied in rabbits. The main results were: (a) Diamine oxidase activity decreased by 60% after intestinal ischemia and reperfusion. A monoexponential dose-response relationship was found between the specific diamine oxidase inhibitor aminoguanidine and reduced survival time. (b) Plasma histamine levels in the right atrium rose only slightly after ischemia, but considerably during reperfusion of the gut, and remained high for at least 20 min. In sham-operated animals the plasma histamine concentration was unchanged throughout the experiment. The histamine content in the intestinal wall did not fall significantly at any time after mesenteric artery occlusion and reperfusion. (c) The aminoguanidine-induced reduction in survival time was completely reversed by pre-treatment of the animals with the H1-receptor antagonist dimethylpyridine and the H2-receptor antagonist cimetidine. This study provides strong evidence for the protective role of intestinal diamine oxidase in intestinal ischemia.