Acid secretion and mobilization of gastric mucosal histamine on combined cholinergic and pentagastrin stimulation

The inhibition of salivary secretion by histamine H2-antagonists--a study on the cat submandibular gland

The aim of the present work was to establish whether the secretory process can be influenced by histamine H2-receptor antagonists, burimamide and metiamide. These drugs were applied intravenously and the secretion was evoked by the electrical stimulation of the chorda tympani nerve or by carbachol (i.v.). In addition to the measurements of the flow of saliva, the blood flow through the gland was measured in some experiments. Both H2-antagonists significantly reduced the rate of salivary secretion induced by the chorda tympani stimulation. The experiments with burimamide did not permit the calculation of dose-response relationship. From the experiments with metiamide the ED50 was 4.6 mumols/kg and Emax was 30% reduction of secretion. The secretory response to carbachol was not diminished by burimamide. In addition to the effect of metiamide on salivation, the reduction of the blood flow through the gland was observed: the effect on the blood flow was significantly smaller, and slower in onset, than the effect on salivation. These results support the hypothesis that H2-receptors are involved in the process of salivary secretion. Histamine effects on glandular elements seem to be more significant than its effect on the blood vessels.

The effect of highly selective vagotomy on the relationship between gastric mucosal blood flow and acid secretion in man

Previous work has shown that the duodenal ulcer population can be defined by a lower ratio between gastric mucosal blood flow and acid secretion (during pentagastrin stimulation) than is found in normal subjects. The results of the present investigation have shown that the ratio is restored to normality by highly selective vagotomy. This suggests that increased tonic activity of the vagus on the parietal cell is one of the important disorders in duodenal ulceration.

Histamine and peptic ulcer: a prospective study of mucosal histamine concentration in duodenal ulcer patients and in control subjects suffering from various gastrointestinal diseases

In a prospective study the histamine content of the mucosa of the body of the stomach was measured in 100 patients consisting of control subjects, patients with duodenal ulcer and patients suffering from various gastrointestinal diseases. The histamine content was found to be 43 mug/g in male control subjects (median) while in duodenal ulcer patients levels attained were significantly lower by about 30 per cent. In all the other groups of patients histamine concentrations in gastric mucosa were found to be "normal". Since in most species it is extremely diffcult to alter the mucosal histamine concentration by any form of treatment, the diminished histamine content of the gastric mucosa in patients with duodenal ulcer seems remarkable. Among several possible explanations offered for this finding we think the most likely is that histamine release is increased in duodenal ulcer disease.

Further studies on the mode of action of isoprenaline on gastric secretion in the conscious rat

1 The effect of isoprenaline on gastric secretion evoked by various means has been studied in conscious rats provided with Pavlov and Heidenhain pouches. 2 Interdigestive acid secretion in the Pavlov pouch was reduced by isoprenaline, whereas pepsin secretion was unaltered. 3 Central vagal stimulation effected by 2-deoxy-D-glucose injection evoked a gastric secretory response that was substantially reduced by isoprenaline. 4 2-Deoxy-D-glucose increased the mobilization of gastric mucosal histamine, an effect that was prevented by isoprenaline. 5 Isoprenaline infusion alone induced a slight increase in histamine mobilization and also a considerable elevation of immunoreactive serum gastrin concentration. 6 The secretory response to food in the Pavlov pouch was almost abolished by isoprenaline. 7 Although the acid response to histamine in the Heidenhain pouch was susceptible to isoprenaline inhibition, that to methacholine was not. 8 Pepsin secretion in the Heidenhain pouch preparation stimulated by histamine or methacholine seemed to be enhanced by isoprenaline.

Effects of secretagogues on oxygen consumption, aminopyrine accumulation and morphology in isolated gastric glands

A recently developed method to isolate gastric glands from the rabbit gastric mucosa (Berglindh and Obrink 1976) was used to study the effects of some common gastric secretagogues. Three parameters were investigated: 1) Respiratory activity; 2) Intraglandular accumulation of the weak base aminopyrine; 3) Quantitative morphology of the parietal cells. The following substances were tested: Histamine, cAMP, db-cAMP, aminophylline, carbachol and pentagastrin. The strongest effect was obtained with db-cAMP which dose-dependently stimulated the respiration up to 200%, increased the aminopyrine accumulation 80% and altered the parietal cell morphology from a typically resting to a typically stimulated state. cAMP also stimulated the respiration but was about 10 times less effective on a molar basis than the dibutyryl form. Histamine, like db-cAMP, stimulated the respiration in a dose-dependent manner and strongly increased the aminopyrine accumulation. The morphological changes were, however, not of the same magnitude as after db-cAMP. Aminophylline, tested only for respiratory activity, stimulated the oxygen consumpation moderately. Carbachol induced a transient increase in both the oxygen consumption and in the aminopyrine accumulation with a peak value after approximately 15 minutes for both, but gave no significant morphological alterations. Pentagastrin, finally, was incapable of inducing changes in any of the three parameters. Aminopyrine was also found to accumulate approx. 50 times in unstimulated, morphologically resting glands. This seems to indicate that there might be acid sites already in resting glands.

The role of cholinergic excitation in the formation of histamine within the rat gastric mucosa

In the absence of the antrum, central vagal excitation and distension of the stomach accelerated the rate of formation of gastric mucosal histamine. The effect of vagus stimulation was abolished by truncal vagotomy or atropine whereas that of distension by atropine. After truncal vagotomy, distension was still effective in accelerating the formation of the amine. Furthermore, mucosal histamine formation in the fasting state was reduced by truncal vagotomy and atropine injection.