INFLUENCE OF HISTAMINE RELEASING AGENTS ON GASTRIC ACID SECRETION OF ISOLATED BULLFROG GASTRIC MUCOSA

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Abstract
The influence of histamine releasing agents on gastric acid secretion was studied in isolated bullfrog gastric mucosa preparations. Maximum acid secretory responses in our preparations were obtained by stimulation with tetragastrin (5×10-7 g/ml), histamine (1×10-5 g/ml) and bethanechol (1×10-6 g/ml). Compound 48/80 (1×10-4 g/ml) showed a transient stimulatory action which was followed by a gradual depression of basal acid secretion. The stimulatory phase of compound 48/80 was completely antagonized by burimamide (1×10-5 g/ml), a histamine H2-receptor antagonist. In gastric mucosa preincubated with compound 48/80, the secretagogue action of tetragastrin or bethanechol was not exerted, although this preparation continued to respond to histamine. The effects of Triton X-100, decylamine and polymixin B were quite similar to those of compound 48/80. After pretreatment with compound 48/80, the gastric mucosa preparation became refractory to the stimulatory action of compound 48/80 or Triton X-100. It is thus suggested that endogenous histamine may play an important role in the secretagogue action of tetragastrin and bethanechol.