Histamine in canine gastric tissues

Luminal regulation of normal and neoplastic human EC cell serotonin release is mediated by bile salts, amines, tastants, and olfactants

Mechanisms by which gut luminal content regulates secretion and motility are ill understood. We evaluated whether neuroendocrine enterochromaffin (EC) cells act as luminal sensors for a wide variety of nutrients and defined the secretory mechanisms of this process. Pure (98-99%) FACS-sorted human EC cells and neoplastic EC cells (KRJ-I) were studied. RT-PCR identified transcripts for T2R1 (bitter), OR1G1 (class II olfactory) and trace amine (TAR1) G protein-coupled receptors (GPCRs) and transporters for glutamine (SNAT1/2), glucose (GLUT1/3/SGLT1), and bile salts (ABST). Glutamine and sodium deoxycholate stimulated 5-HT release (EC(50) = 0.002-0.2 microM; 2-fold release) but were 10-100 times more potent in neoplastic EC cells, which also secreted 6-13 times more 5-HT. Tastants (caffeine, tyramine, octopamine) and olfactants (thymol and eugenol) also stimulated normal and neoplastic EC cell 5-HT secretion (EC(50) = 1.2 nM to 2.1 microM and 0.05 nM to 0.1 microM release, respectively); 2-deoxyglucose and the artificial sweetener sucralose also stimulated (EC(50) = 9.2 and 0.38 nM). 5-HT release was associated with ERK phosphorylation (1.5-fold, P < 0.02) and could be inhibited by a somatostatin analog (IC(50) = 1 pM). Eleven secretory associated genes including the vesicle docking inhibitor STXBP3 were upregulated in response to glutamine and bile salt stimulation in neoplastic EC cells. Targeting STXBP3 expression by use of antisense knockdown significantly (P < 0.05) reduced 5-HT secretion. In conclusion, EC cells express GPCRs and transporters for luminal tastants, olfactants, glutamine, glucose, and bile salts. Activation includes a panel of secretory genes, ERK phosphorylation, and 5-HT secretion. Luminal EC cell regulation is likely to be as important as G cell regulation in gastric acid secretion; development of agents to target EC cell function is therefore a critical therapeutic goal.

Influence of histamine releasing agents on gastric acid secretion of isolated bullfrog gastric mucosa

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 X 10(-7) g/ml), histamine (1 X 10(-5) g/ml) and bethanechol (1 X 10(-6) g/ml). Compound 48/80 (1 X 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 X 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.

The Bayliss-Starling lecture 1973. The gastrointestinal hormones: a review of recent advances

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Distribution of histamine in the mucosa of the gastrointestinal tract of the dog

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