Induction by interleukin-1, tumor necrosis factor and lipopolysaccharides of histidine decarboxylase in the stomach and prolonged accumulation of gastric acid

1. Injection of interleukin-1 (IL-1) into pylorus-ligated rats has been shown strongly to inhibit gastric secretion. However, in the present study, we found that an intraperitoneal injection of IL-1 into intact (non-pylorus-ligated) fasted mice rapidly (within 30 min) induced an accumulation of gastric acid (`early response''). When the dose of IL-1 was larger, the accumulation lasted for a longer period.
2. Injection of IL-1 also caused a later elevation of the activity of histidine decarboxylase (HDC), the histamine-forming enzyme, in the stomach (`later response'').
3. Cimetidine, an antagonist of histamine H₂-receptors, suppressed the accumulation of gastric acid in both the early and later periods. An irreversible inhibitor of HDC, α-fluoromethylhistidine, partially inhibited the accumulation in the later period.
4. IL-1, when injected 1 h after feeding in mice fasted overnight, markedly retarded gastric emptying.
5. Tumour necrosis factor (TNF) and lipopolysaccharide (LPS) or endotoxin from E. coli both had IL-1-like effects on the stomach, and their effects are presumably mediated by IL-1.
6. These results support the idea that an inhibition of gastric emptying and an elevation of HDC activity in the stomach may explain the findings that a long-lasting accumulation of gastric acid is induced by IL-1 despite its potent inhibition of gastric acid secretion.
7. On the basis of these results, and in the light of the known actions of histamine, the possible roles of IL-1 in gastric inflammation and ulceration are discussed.