Effect of parietal cell vagotomy on acid secretory responsiveness to circulating gastrin in humans. Relationship to postprandial serum gastrin concentration

Intracisternal TRH analog increases gastrin release and corpus histidine decarboxylase activity in rats

Thyrotropin-releasing hormone (TRH) acts in brain stem nuclei to induce vagally mediated stimulation of gastric secretion. The effects of intracisternal injection of the TRH analog RX-77368 on plasma gastrin levels and corpus histidine decarboxylase (HDC) activity were studied in 48-h fasted conscious rats. RX-77368 (25-100 ng) increased plasma gastrin levels by threefold at 30 min, which remained significantly higher than control at 2 and 4 h postinjection. Corpus HDC activity began to increase at 2 h and reached a peak at 4 h postinjection with a 21-fold maximum response observed at 50 ng. Morphological changes in the appearance of corpus HDC-immunoreactive cells correlated well with HDC activity. Pretreatment with gastrin monoclonal antibody completely prevented RX-77368 stimulatory effects on HDC activity. Atropine significantly attenuated gastrin increase at 30 min by 26%. These results indicated that in conscious fasted rats, TRH analog acts in the brain to increase corpus HDC activity in the enterochromaffin-like cells, which involves gastrin release stimulated by central TRH analog.

Gastric acid secretion and intragastric acidity: measurement in health and disease

Gastric acid secretion tests have limited use in clinical practice. For practical purposes, a pH measurement on a fasting gastric aspirate will provide strong evidence of the presence or absence of achlorhydria. Tests of gastric acidity, in particular 24-h acidity studies, have provided considerable insight into normal and abnormal gastric physiology, and have largely determined the dosing regimens for the management of acid-peptic diseases. Acid tests may be simple to perform, so much so that they have been suggested as 'practicals' for student teaching (Nicol et al, 1991). However, reproducible and meaningful results require careful attention to detail, and the appropriate mathematical analysis is still subject to some debate. It is important that the presentation of the data should allow the reader to assess the response over the 24-h period, and also the range of individual responses. Despite the many years of research into gastric acid secretion, only recently have the effects of age, sex, diet, smoking and mental stress been identified. In addition, many data need to be reviewed in the light of the effects of H. pylori infection on gastrin release. H2-receptor antagonists had been studied extensively before and since their first clinical use in 1974, but surprisingly only recently have the issues of tolerance and rebound been defined. The 24-h intragastric acidity profile remains an essential study before the start of clinical trials on any new drug to be used for the treatment of acid-peptic diseases.

Effect of age on gastric acid secretion and serum gastrin concentrations in healthy men and women

The effects of age on basal, meal-stimulated, and human gastrin-17-stimulated gastric acid secretion rates and serum pepsinogen concentrations were evaluated in 41 healthy men and women. Older subjects (ages 44-71 years; mean, 57 years) had higher mean basal, meal-stimulated, and gastrin-17-stimulated acid secretory rates and basal serum pepsinogen I and II concentrations than younger subjects (ages 23-42 years; mean, 33 years). Age-related differences in acid secretion were especially prominent in men, and age-related differences in serum pepsinogen I and II concentrations were more prominent in women. Higher gastric acid secretion rates in older subjects could not be explained by body size (height, weight, body surface area, or fat-free body mass) or by the higher incidence of infection with Helicobacter pylori. Using a multivariate linear regression model, age had an independent positive effect on acid secretion, and H. pylori infection had an independent negative effect. It was concluded that aging is associated with an increase in gastric acid secretion in humans, especially in men, while infection with H. pylori is associated with lower acid secretion rates.

Elevated gastric acid secretion in patients with Barrett's metaplastic epithelium

Gastric acid secretion in response to a protein meal and to exogenously administered synthetic human gastrin 17-I was measured in patients with Barrett's esophagus, patients with uncomplicated gastroesophageal reflux, and normal age- and sex-matched controls. Acid secretion, both basally and in response to gastrin 17-I, was significantly greater in patients with Barrett's esophagus compared to normal individuals without reflux. Basal gastrin levels and meal-stimulated levels of the hormone were similar among all three groups. Sensitivity to gastrin, expressed as the concentration causing half-maximal acid secretion, was also similar among the study groups. It is speculated that elevated basal acid production in Barrett's esophagus may contribute to the pathogenesis of the disorder.

Current status of proximal gastric vagotomy

Proximal gastric vagotomy is nearing its twentieth year in clinical use as an operation for peptic ulcer disease. No other acid-reducing operation has undergone as much scrutiny or study. At this time, the evidence of such studies and long-term follow-up strongly supports the use of proximal gastric vagotomy as the treatment of choice for chronic duodenal ulcer in patients who have failed medical therapy. Its application in treating the complications of peptic ulcer disease, which recently have come to represent an increasingly greater percentage of all operations done for peptic ulcer disease, is well-tested. However, initial series suggest that it should probably occupy a prominent role in treating some of these complications, particularly in selected patients, in the future. The operation has the well-documented ability to reduce gastric acid production, not inhibit gastric bicarbonate production, and also minimally inhibit gastric motility. The combination of these physiologic results after proximal gastric vagotomy, along with preservation of the normal antropyloroduodenal mechanism of gastrointestinal control, serve to allow patients with proximal gastric vagotomy the improved benefits of significantly fewer severe gastrointestinal side effects than are seen after other operations for peptic ulcer disease.

Effect of proximal gastric vagotomy on calculated gastric HCO3- and nonparietal volume secretion in man. Studies during basal conditions and gastrin-17 infusion

We calculated gastric HCO3- and H+ secretion, as well as nonparietal and parietal volume secretion, in 15 duodenal ulcer patients who had previously undergone successful proximal gastric vagotomy, 15 unoperated duodenal ulcer patients, and 15 normal control subjects. Basal HCO3- secretion was not significantly altered after vagotomy, while basal H+ secretion, parietal volume and nonparietal volume secretion were reduced significantly. Intravenous gastrin-17 infusion reduced gastric HCO3- secretion by approximately 50% in both unoperated ulcer patients and normal subjects (P less than 0.05). Gastrin-17 infusion did not inhibit gastric HCO3- secretion after vagotomy. In fact, mean gastric HCO3- secretion increased to a nearly significant extent in response to gastrin (P = 0.06). These findings indicate that gastrin inhibits gastric HCO3- secretion in humans and that the gastrin-induced reduction in gastric HCO3- secretion is dependent upon intact vagal innervation to the oxyntic mucosa.

Should it be parietal cell vagotomy or selective vagotomy-antrectomy for treatment of duodenal ulcer? A progress report

This is a progress report of a prospective, randomized study involving 200 consecutive patients treated electively with either parietal cell vagotomy (PCV) or selective vagotomy and antrectomy (SV-A). Both groups comprised patients with pyloric, prepyloric, or duodenal ulcers. There was no operative mortality in either group. Patients were examined at 2, 6, 12 months, and every 12 months thereafter for 8-10 years. The two operations produced no statistical difference in the frequency of diarrhea. Dumping (p less than 0.0005) and weight loss (p less than 0.0005-p less than 0.05) were statistically less after PCV than after SV-A. There were two recurrent ulcers (2.2%) after SV-A. One was treated successfully by medical therapy and one patient suspected of having gastrinoma had total vagotomy. Nine patients had recurrent ulcers in the PCV group for an accumulated recurrence rate of 10.1% at 10 years by life-table analysis. There was a significant difference (p less than 0.033) between the curves for recurrent ulcers in the two groups of patients. The recurrent ulcer rate after PCV was 21% for patients with pyloric and prepyloric ulcers and 6% for patients with duodenal ulcer. There was no significant difference between the recurrent ulcer rate for PCV and SV-A if the patients with pyloric and prepyloric ulcers were withdrawn from the study. Of the nine patients with recurrent ulcers in the PCV group, three had an inadequate vagotomy and four had a pyloric or prepyloric ulcer before operation. Three patients were successfully treated with antrectomy. Five patients were treated successfully by medical therapy and remained healed for long periods without recurrence. One patient had five recurrences. He declined operation and remained free of symptoms for 3 years after his last recurrence. Poor gastric emptying necessitated gastroenterostomy in five patients in the SV-A group and in one patient in the PCV group. Patients' clinical results were evaluated according to a simple Visick grading scale. A significantly (p less than 0.0005) greater number of patients were in Visick I category after PCV than after SV-A. The clinical results obtained with PCV make this the operation of choice for the elective surgical treatment of duodenal ulcers even though the results obtained with SV-A were good.

Variable contribution of gastrin to gastric acid secretion after a meal in humans

The purpose of these experiments was to determine the contribution of gastrin to the acid secretory response to eating in healthy human subjects. To simulate the gastric and intestinal phases of eating, a meal was homogenized and then infused into the stomach through a nasogastric tube. At the same time, the cephalic phase of acid secretion was activated by sham feeding. With this simulated meal, mean serum gastrin concentration increased from a basal value of 43 +/- 9 pg/ml to an average postprandial gastrin concentration over 2 h of 121 +/- 25 pg/ml. Gastrin release after this simulated meal was similar to gastrin release after a normally eaten meal in the same 12 subjects. Gastric acid secretion in response to the simulated meal, which was measured by in vivo intragastric titration, averaged 24.2 +/- 2.4 mmol/h. To determine how much of this postprandial acid secretion could be attributed to gastrin, gastrin 17 I was infused intravenously in the same subjects on a separate day and acid secretion and serum gastrin concentrations were measured. By relating serum gastrin concentration during gastrin 17 infusion to concomitant acid secretion, we determined that an average postprandial serum gastrin concentration of 121 pg/ml could result in an acid secretion rate of 21.5 mmol/h, 89% of the actual acid secreted after the simulated meal in these subjects. However, in individual subjects, the amount of gastrin released after a meal could produce as little as 51% or as much as 162% of actual postprandial acid secretion. Thus, in individual human subjects the contribution of gastrin to acid secretion after a meal is variable.

Effect of sham feeding on acid secretion in patients with Zollinger-Ellison syndrome with or without proximal gastric vagotomy

In dogs, vagal stimulation by sham feeding inhibits gastrin-stimulated gastric acid secretion from vagally denervated fundic pouches. To investigate this in humans, we sham fed patients with endogenous hypergastrinemia secondary to the Zollinger-Ellison syndrome. Whether these patients had been treated previously by proximal gastric vagotomy or not, sham feeding did not reduce basal acid secretion. Thus, sham feeding did not inhibit acid secretion in humans with hypergastrinemia, even when the fundus of the stomach had been vagally denervated.

The antral gastrin-producing cells in duodenal ulcer patients. A study of preoperative G-cell densities, fasting serum-gastrin, pre- and postoperative gastric acid secretion and outcome after parietal cell vagotomy

Antral gastrin-producing cell densities, as well as serum gastrin and gastric acid secretion were obtained prior to parietal cell vagotomy from 60 patients suffering from chronic duodenal ulcer disease. Acid secretion was also measured postoperatively. The patients were followed for five years. The ulcer recurrence rate was 20%. No differences were found in the G-cell densities, fasting serum-gastrin or gastric acid secretion preoperatively between the two groups: recurrence and non-recurrence. The acid secretion was higher postoperatively in patients with recurrent ulcer as compared to those without recurrence of the ulcer, suggesting that incomplete vagotomy is a reasonable explanation of the recurrence, even though post-operative G-cell abnormality cannot definitely be ruled out.