A comparative study of the effects of gastrin, histamine, histalog, and mechothane on the secretory capacity of the human stomach in two normal subjects over 20 months

Pentapeptide infusion test

Pentapeptide infused intravenously in graded doses provoked at a dose of 1.5 microg per kg per hour a peak HCl output, which was significantly higher than the HCl secretion induced by intravenous histamine in a dose of 40 microg per kg per hour in five healthy subjects. Pentapeptide infusion test at a dose of 1.5 microg per kg per hour appears to be a very reproducible and safe mode of gastric stimulation, giving a sustained and high level of gastric secretion in 20 subjects, including 10 healthy men and 10 duodenal ulcer patients. Infusion test with pentapeptide has some advantage over histamine stimulation in so far as it is safe, and almost completely free of side-effects. No difference in the response curves to pentapeptide and histamine was found between the normal subjects and duodenal ulcer patients.

Effects of Helicobacter pylori on gastritis, pentagastrin-stimulated gastric acid secretion, and meal-stimulated plasma gastrin release in the absence of peptic ulcer disease

OBJECTIVE

There is strong evidence accumulating that chronic infection with Helicobacter pylori (H. pylori) interferes with inhibitory pathways of the regulation of acid secretion. The increase in maximum acid output (MAO), and the increase in the sensitivity of the parietal cell to gastrin commonly observed in patients suffering from duodenal ulcer disease (DU), however, remains largely unexplained. Insufficient evidence is available concerning how these parameters are influenced by H. pylori infection in patients not suffering from peptic ulcer disease (PUD) and how they are related to H. pylori-induced gastritis. The aim of this study was to compare basal gastric acid secretion (BAO), MAO, and the sensitivity of the parietal cell to gastrin in H. pylori-positive and H. pylori-negative patients not suffering from PUD, and to study the relationship with their individual postprandial gastrin release and the degree of gastric antral and corpus gastritis.

METHODS

H. pylori status was assessed by CLO test and histology (two biopsies each from the antrum and the corpus) in 14 H. pylori-positive and 16 H. pylori-negative nonulcer patients of comparable age, weight and gender. Gastritis score was assessed by a pathologist, who was unaware of the acid secretory data. Following determination of BAO, the relation of pentagastrin and gastric acid secretion was established with a cumulative pentagastrin dose response curve for the dose range 0.03-6.0 microg/kg(-1) h(-1) and MAO (Vmax) and pentagastrin sensitivity (ED50) were determined. Basal and postprandial gastrin release was measured by radioimmunoassay.

RESULTS

There was a significant higher gastritis score in the H. pylori-positive compared with the H. pylori-negative subjects. The dose response curves of the pentagastrin stimulated gastric acid secretion were not different between H. pylori-positive and H. pylori-negative groups. No correlation was seen between the gastritis score, basal acid output (BAO) peak acid output (PAO), maximum acid output (MAO), ED50 values and the plasma gastrin values. There was, however, a considerable larger variation of the PAO and MAO data of the H. pylori-infected subjects and >50% of the respective data was above or below the relatively low range of the respective values of the noninfected subjects.

CONCLUSIONS

H. pylori-induced gastritis does not regularly enhance maximum acid output in nonulcer patients, nor does it modify the sensitivity of the parietal cell to gastrin. H. pylori infection is thus unlikely to be directly responsible for an increase of these parameters in DU disease. Our data support, however, the concept that chronic H. pylori infection can either enhance or attenuate maximum acid secretory capacity in certain subgroups of patients.

Optimizing acid suppression for treatment of acid-related diseases

Gastric acid is of central importance in the pathogenesis of duodenal ulcer, gastric ulcer, and gastroesophageal reflux disease. Pharmacological reduction of acid secretion is, therefore, the mainstay of current treatment, but the optimal degree of acid suppression remains incompletely understood. This paper considers the ideal ways of assessing and reporting the pharmacological effectiveness of acid-inhibiting drugs and relating such data to clinical efficacy. Twenty-four-hour intragastric pH measurements are widely used for this purpose, although this technique cannot measure secretion quantitatively. Data on suppression of 24-hr intragastric acidity for groups of subjects have been successfully correlated with healing rates for duodenal ulcer, gastric ulcer, and gastroesophageal reflux disease. Three primary determinants of healing have been derived from antisecretory data. These are the degree of suppression of acidity, the duration of suppression of acidity, and the duration of treatment. The order of importance of these determinants varies depending on the disease. Data on 24-hr intragastric acidity should be accompanied whenever possible by data on 24-hr plasma gastrin levels, as the relationship between suppression of acidity and a rise in gastrin varies widely between individuals. It is not possible to predict the plasma gastrin level from the intragastric pH or any other measurement of intragastric acidity. Comparative data sets in groups of subjects may provide useful information. Proton pump inhibitors produce a greater and longer-lasting degree of suppression of acidity than conventional doses of H2-receptor antagonists. For this reason, they are more effective in healing duodenal ulcer and gastric ulcer. However, in view of the importance of duration of treatment, healing rates with the H2-receptor antagonists approach those obtained with proton pump inhibitors if treatment is continued for a longer time. In gastroesophageal reflux disease in particular, although the optimal degree of acid suppression is not yet defined, the consistently superior performance of proton pump inhibitors demonstrates that increased suppression of acidity is clinically beneficial.

Effects of fundic vagotomy and cholinergic replacement on pentagastrin dose responsive gastric acid and pepsin secretion in man

The effects of fundic vagotomy on acid and pepsin secretion in 12 patients (10 males, two females; nine duodenal ulcer, three gastric ulcer) were studied using a pentagastrin dose response before and after Vagotomy. In the intact stage H, Cl, and pepsin output all had the same ED50, 120-127 pmol/kg/h. Vagotomy reduced basal output of acid by 78%, Cl- by 50%, and pepsin by 62%. Postvagotomy basal outputs were not related to preoperative levels, while maximum acid output was reduced by an average of 35%, proportionally to the preoperative output (r = 0.94). Vagotomy uncompetitively (ED50 increase, Vmax decrease) inhibited the pentagastrin dose response of acid, chloride, and pepsin output. Postoperatively, a six-fold greater dose of pentagastrin (450 vs 76 pmol/kg/h) was required to stimulate acid to 50% of its preoperative maximum output. For pepsin secretion the increase was 12-fold (185 vs 15 pmol/kg/h). In five of the nine duodenal ulcer patients pentagastrin dose responses were repeated with a background infusion of urecholine, 20 micrograms/kg/h. Urecholine increased basal and peak acid, pepsin, and chloride outputs, and the ratio of basal: maximal almost to prevagotomy levels; it also restored the sensitivity to pentagastrin. Serum gastrin was not significantly changed by urecholine or by vagotomy. We conclude that the level of basal acid and pepsin secretion in ulcer patients, which is largely eliminated by vagotomy, is dependent on the vagus and not on serum gastrin. The effects of vagotomy are functional, are due to cholinergic withdrawal, and usually can be restored by cholinergic replacement.

Gastric acid secretion

Advances in the understanding of physiologic control of gastric secretion raise the hope that an effective nonsurgical therapy for peptic ulcer disease will be developed soon. This paper reviews these advances with special emphasis upon those aspects of hormonal control, cyclic nucleotide function, and histamine activity which may have therapeutic applications.

Rat gastric acid secretion studies with histamine and synthetic gastrin-like pentapeptide

1. Gastric acid secretion was measured in the urethane anaesthetized rat whilst maintaining a recirculated gastric perfusion fluid at pH 4.2. The latent period of onset of secretion following single intravenous doses of histamine and pentapeptide in combination was significantly shorter than that following either stimulant alone.3. When administered over a period of 2 hr the maximal steady rate of secretion in response to pentapeptide was 75% of that to histamine.4. Acid stimulatory effects were additive both when the drugs were given concurrently over a 2 hr period and when one was administered after a maximal response had been obtained to the other.5. Although there is some evidence to indicate that histamine and pentapeptide might be initiating acid secretion by different mechanisms it is suggested that they may not be acting with total independence.

Highly selective vagotomy without a drainage procedure in the treatment of duodenal ulcer

A consecutive series of 25 patients with chronic duodenal ulcer has been treated by highly selective vagotomy without a drainage procedure. The vagal fibres passing to the distal 5–7 cm. of the stomach—the nerves of Latarjet—were left intact, as were the hepatic and coeliac branches of the vagus. The object was to denervate only the parietal cell mass, while preserving normal gastric emptying and normal inhibition of gastric secretion from the antrum and duodenum. This operation should cure the ulcer as effectively as vagotomy with drainage does, and at lower cost in terms of side-effects such as dumping and diarrhoea.

The insulin test was negative in each case, suggesting that vagal denervation of the parietal cell mass was complete. Evidence provided by mucosal biopsies taken at operation does not fully support this view, however. Pentagastrin-stimulated acid output was reduced by 70 per cent, and pepsin output by 51 per cent, 3 months after operation. The volume of resting juice was halved and spontaneous acid output was reduced by 97 per cent at this time. Thus, highly selective vagotomy is as effective as truncal or bilateral selective vagotomy with drainage in reducing gastric acid output in the early months after operation.

There have been no deaths. With 2 exceptions, the patients appear to be doing well clinically and few complain of side-effects, but the period of follow-up is only from 3 to 11 months.

These results are encouraging. They suggest that a highly selective vagotomy, denervating the parietal cell mass but leaving the antrum innervated, may be all that is required to cure most patients who have a chronic duodenal ulcer.

Effect of glycopyrronium bromide on basal, and histamine- or gastrin-induced gastric secretion

Acid secretory responses were obtained in rats given either intravenous histamine as dihydrochloride or gastrin subjected to partial purification. A continuous recording method for measuring gastric acid secretion was used. When the rat stomach was perfused with weak sodium hydroxide solution, glycopyrronium bromide (a powerful anticholinergic drug) blocked the acid gastric secretory effects of both histamine and gastrin. Glycopyrronium bromide in doses of 2 μg/100 g body weight of rat is well tolerated. Doses higher than 2 mg/100 g caused respiratory disturbances. The action of glycopyrronium bromide in blocking the gastric secretory effects of gastrin supports the hypothesis that gastrin acts partly by stimulating the vagus nerve.

Factors affecting maximal acid secretion

The mechanisms by which different factors affect the maximal acid secretion of the stomach are discussed with particular reference to nationality, sex, age, body weight or lean body mass, procedural details, mode of calculation, the nature, dose and route of administration of a stimulus, the synergistic action of another stimulus, drugs, hormones, electrolyte levels, anaemia or deficiency of the iron-dependent enzyme system, vagal continuity and parietal cell mass.

Specific stimulation of gastric acid secretion by a pentapeptide derivative of gastrin

The effects of gastrin, a synthetic pentapeptide (N-t-butyloxycarbonyl-β-Ala. Try. Met. Asp. Phe. NH2; I.C.I. 50,123) and histamine on the secretion of gastric acid have been compared in a perfused stomach preparation using anaesthetised rats. The pentapeptide was shown to possess similar secretory activity to that of gastrin but to be 11 times less potent on a molar basis. It produced acid secretions similar to those produced by histamine when compared in several different ways. Unlike histamine, the pentapeptide was without significant effect on blood pressure or haematocrit in maximally stimulating doses.