title: Histamine and acid gastric secretion in the rat
Creators: name: Main, I. Harvey M.
Publisher: name: University of Edinburgh
Year: 1961
Subjects: subject: Histamine
subject: Acid Secretion
subject: Stimulants
subject: Inhibitors
subject: Parasympathomimetic Drugs

description: Acid Secretory Stimulants: (1) A relationship exists between the output of free histamine and total acid in rat gastric secretion stimulated in various ways. (2) During stimulation by histamine infusion and insulin hypoglycaemia, the relationship is constant, the values of the ratio of histamine output (ng base) over acid output (uequiv. HC1) are 0.86 (±0.34 S.D.), during histamine infusion, and 1.29 (±0.44 S.D.), during insulin hypoglycaemia. There is sore histamine in relation to acid in gastric secretion of the rat than in dog and cat. (3) During stimulation by the parasympathomimetic drugs, carbachol and pilocarpine, there is a changing relationship between outputs of histamine and acid, the ratio falling at higher levels of secretion. (4) Although there is insufficient evidence to draw conclusions concerning the nature of the relationship between histamine and acid, gastrin is a potent secretory stimulant in the rat. (5) So increase in histamine output occurred when the lumen of the stomach was perfused with acid. (6) The source of the histamine appearing in gastric secretion has not been established, though the graphs of acid output and histamine output plotted against histamine infusion rate, suggest that such histamine is the same as that infused and is not of local origin. Acid Secretory Inhibitors: (7) Acetazoleamide inhibited histamine induced acid secretion without causing a reduction in histamine output. This is further evidence that histamine output is related to the histamine infusion x’ate rather than to the acid output. (8) During secretion induced by methods of stimulation other than histamine infusion, acetazoleamide reduced not only acid output, but histamine output. This suggests that stimulation by parasympathomimetic drugs and insulin does not depend on a general rise in blood plasma histamine content. (9) Atropine abolished secretion induced by parasympathomimetic drugs with a corresponding reduction in histamine output. Inhibition of histamine induced secretion (up to 60%) was also associated with a reduced output of histamine. Aminoguanidine: (10) The inability of aminoguanidine to augment secretion induced by insulin, pilocarpine or carbachol while augmenting histamine induced secretion is further evidence against a rise in plasma histamine. (11) Rat arterial blood plasma contained approximately 10 ng/ml of histamine. During secretion induced by carbachol, insulin or gastrin, there was no significant rise in plasma histamine concentration. During comparable levels of secretion induced by histamine infusion, a 300-fold increase in plasma histamine occurred. This increases the significance of the ratio, histamine to acid output, which is similar during histamine and insulin stimulation. Th® results of this investigation support the theory that histamine has a physiological role in the secretion of acid by the stomach and suggest that its site of action and release is in or near the secretory cells bordering the surface of the gastric mucosa.