Nina Kwiecień

Comparison of Methylated Prostaglandin E2 Analogues Given Orally in the Inhibition of Gastric Responses to Pentagastrin and Peptone Meal in Man

In 32 healthy male volunteers the effects on gastric secretion of three methyl analogues of prostaglandin (PG) E2 have been studied, namel, 15 (R) -15-methyl PGE2 methyl ester, 15 (S) -15-methyl PGE2 methyl ester, and 16, 16-dimethyl PGE2. Secretion was measured for 30 min and a PG analogue at doses ranging from 1.25 to 2.5 mug per kg or a placebo was administered. Gastric secretion was then stimulated either by an intravenous infusion of pentagastrin (2 mug per kg-hr) or by a peptone meal with acid secretion determined by intragastric titration technique. The tests were randomized and double blind. All three methyl PG analogues exhibited a profound and prolonged inhibitory action on gastric acid and pepsin secretion induced by pentagastrin. PG analogues caused almost complete inhibition of gastric acid response to a peptone meal accompanied by a significant reduction in the serum concentration of immunoassayable gastrin. Except with the highest dose of PG (S) -15-methyl PGE2 methyl ester, which caused abdominal discomfort and single episodes of diarrhea in some subjects, no symptoms or untoward biochemical effects were observed. It is concluded that these methylated PG analogues are very potent inhibitors of gastric acid and pepsin secretion stimulated by pentagastrin or a meal and may have clinical potential in the treatment of peptic ulcer.

Effect of Glucagon on Meal-Induced Gastric Secretion in Man

The effect of glucagon on gastric acid and pepsin secretion, basal or stimulated by a meal, pentagastrin and histamine, was studied in duodenal ulcer patients. Intravenous glucagon infused in graded doses ranging from 6.2 to 50 mug per kg-hr produced a dose-related inhibition of pentagastrin-induced acid secretion reaching about 40% of the control level at the dose of 50 mug per kg-hr. Acid inhibition was paralleled by a decrease in the pepsin output and serum calcium level and was accompanied by a rise in the blood glucose concentration. Glucagon used in a standard dose of 25 mug per kg-hr produced about 50% inhibition of acid secretion induced by a meal (measured by intragastric titration) accompanied by a significant decrease in the serum gastrin level measured by radioimmunoassay. Histamine-induced secretion was only slightly inhibited by glucagon, and the degree of inhibition for acid (25%) and pepsin (20%) secretion was statistically insignificant.

Oral cavity as a potential source of gastric reinfection by Helicobacter pylori

Helicobacter pylori (Hp) is a common pathogen colonizing the a gastric mucosa, but some reports indicated that it may also be found in the oral cavity, which could serve as a reservoir of the bacteria and a source of gastric reinfection. Accordingly, we aimed to study whether the oral cavity, particularly gingival pockets, are colonized by Hp and whether it could be the source of gastric reinfection. We studied 329 patients with dyspeptic symptoms (257 with chronic gastritis, 15 with gastric ulcer, and 57 with duodenal ulcer). The [13C]urea breath test (UBT), gastroscopy, and Hp culture from gastric biopsies were carried out, and material was collected from the oral cavity (gingival pocket) for bacteriological culture and genomic DNA studies. The serum was obtained for anti-Hp IgG and anti-CagA assays and saliva for anti-Hp IgA determination using the ELISA technique. Bacteria in material from gingival pockets and biopsies from the corpus and antrum of stomach of 30 DU patients before and after Hp eradication were also examined by PCR technique, using primers specific for 16S rRNA. All Hp-positive patients (276) were subjected to one week of triple therapy (omeprazole 2 × 20 mg twice a day, clarithromycin 2 × 500 mg twice a day, and metronidazole 2 × 500 mg twice a day). The measurements described above were then repeated at four weeks and six months. Bacteriological culture showed the presence of Hp in the material from oral cavity in about 50% of patients, whereas UBT, used as a gold standard, revealed gastric Hp infection in about 84% of these patients. The eradication was successful in the majority of patients (87%), but about 13% of them were still Hp positive after four weeks and about 21% after six months. Four weeks after Hp therapy, Hp was found in culture from oral samples in 23% (P < 0.05 vs initial) and after six months in 35.1%. The IgA levels recorded in saliva were in a close agreement with UBT results. Hp DNA assessed by PCR in 30 DUs before eradication of Hp was detected in 95% of antral mucosa, 90% in corpus mucosa, and in 35% of gingival pocket material, and after eradication therapy Hp DNA values fell to 25%, 20%, and 10%, respectively. In conclusion, Hp is commonly detected in the oral cavity of patients with dyspeptic symptoms, but the gastric reinfection does not appear to occur in the patients despite oral Hp colonization.

Effect of ranitidine, a new H2-antagonist, on gastric and pancreatic secretion in duodenal ulcer patients

The effects of a new H2-receptor blocker, ranitidine, given intravenously (for comparison with cimetidine) or orally on gastric and pancreatic secretion have been studied in duodenal ulcer patients. Ranitidine appears to be several times more potent and a longer-acting inhibitor of gastric secretion than cimetidine. This H2 blocker does not affect pancreatic bicarbonate and enzyme secretion.

Luminal Nα-methyl histamine stimulates gastric acid secretion in duodenal ulcer patients via releasing gastrin

Nalpha-methyl histamine is an unusual histamine metabolite which is produced in the stomach infected by Helicobacter pylori and which was shown in animals to stimulate gastric acid secretion and to release gastrin in vitro isolated G-cells, but no information is available regarding its influence on gastric secretion and gastrin release in duodenal ulcer patients before and after H. pylori eradication. In this study, we compared the effects of intragastric administration of single or graded doses of Nalpha-methyl histamine on gastric acid secretion and plasma gastrin levels in 16 male duodenal ulcer patients (aging from 35 to 48 years and weighing 65-82 kg) before and after the eradication of H. pylori. Furthermore, the gastric luminal histamine and gastrin contents were determined before and after H. pylori eradication. In H. pylori-infected duodenal ulcer patients, the intragastric application of Nalpha-methyl histamine failed to affect gastric acid secretion or plasma gastrin levels. Following eradication of H. pylori, gastric luminal histamine and gastrin, and both basal gastric acid secretion and plasma gastrin levels, were significantly reduced. Nalpha-methyl histamine given intragastrically in graded doses to such H. pylori-eradicated duodenal ulcer patients was found to increase dose-dependently gastric acid output reaching at a dose of 5 mg, about 80% of histamine maximum induced by i.v. infusion of 25 microg/kg h of histamine dihydrochloride. We conclude that Nalpha-methyl histamine is a potent luminally active stimulant of gastrin release and gastric acid secretion in H. pylori-eradicated patients when luminal histamine is low but is not effective in H. pylori infected patients when luminal histamine is enhanced, possibly due to desensitization of gastrin (G-cells) and acid-producing (parietal) cells by Nalpha-methyl histamine produced excessively in H. pylori-infected stomach.

Mechanisms of the Inhibitory Action of Prostaglandins on Meal-Induced Gastric Secretion

In dogs with gastric fistula and Heidenhain pouch (HP), 15(S)-15-methyl prostaglandin E2 methyl ester (PG-S) infused intravenously in graded doses (0.5--2.0 microgram/kg/h) inhibited dose-dependently, meal-induced acid secretion both from the vagally innervated main stomach and from the HP. This inhibition was associated with a marked reduction in mucosal blood flow but without significant change in the ratio of aminopyrine concentration in the gastric juice and blood plasma, indicating that the reduction in gastric microcirculation was probably secondary to the inhibition of gastric secretion. In dogs with special cannulae that allowed complete separation of the stomach and the intestine, PG-S caused stronger inhibition of gastric acid and serum gastrin responses to gastric and intestinal meals after application directly to the gastric mucosa, than following duodenal administration. PG-S applied topically to the HP mucosa also suppressed direct chemical stimulation of the HP by L-histidine meal. We conclude that PG-S exerts its inhibitory action on gastric secretion both by local contact with the mucosa via suppression on gastrin release from the antral G-cells and by direct inhibition of the secretory activity of the oxyntic glands.

Effect of methylated PGE2 analogs given orally on pancreatic response to secretin in man

The effect of two methylated PGE2 analogs given orally on the pancreatic response to intravenous secretin has been studied in 8 healthy subjects. The secretion of bicarbonate was not changed by these PGE2 analogs. The secretion of enzymes during infusion of PGE2 analogs was significantly greater than in the control.

Dynamics of Gastric Acid Inhibition by Ranitidine in Duodenal Ulcer Patients

The dynamics of the inhibitory effect of ranitidine, a new H2-receptor antagonist, on histamine and pentagastrin-induced gastric secretion have been examined in duodenal ulcer patients. The inhibition by ranitidine of histamine-induced secretion was found to be competitive, whereas that of pentagastrin-induced secretion not competitive. Ranitidine was an effective inhibitor of pentagastrin-induced secretion for 8-12 h after administration. The availability of ranitidine, a powerful and long-acting inhibitor of gastric secretion, provides an opportunity of an alternative treatment from cimetidine for peptic ulcer and related diseases.

Effect of synthetic 15-methyl analog of PGE2 on gastric acid and serum gastrin response to peptone meal, pentagastrin, and histamine in duodenal ulcer patients

The effect of 15(S)-15-methyl PGE2, methyl ester (15-ME-PGE2), used intravenously in a standard dose of 0.5 μg/kg-hr on gastric secretion and serum gastrin level was studied in 6 duodenal ulcer patients. 15-Me-PGE2 caused an immediate and almost complete inhibition of basal gastric acid and pepsin secretion. Acid secretion induced by a peptone meal and determined by intragastric titration technique was almost as high as the maximal response to histamine and accompanied by a significant rise in serum concentration of immunoassayable gastrin. 15-Me-PGE2 caused a sudden and complete inhibition of gastric acid response to a peptone meal. 15-Me-PGE2 did not significantly affect serum gastrin levels both under basal conditions and in response to a peptone meal. Gastric acid and pepsin outputs induced by maximal stimulation with pentagastrin (4 μg/kg-hr) was inhibited by 15-Me-PGE2 by about 70% and that induced by histamine by about 45%. After the with-drawal of 15-Me-PGE2 infusion, gastric secretion remained reduced for the remainder of the test. We concluded that 15-Me-PGE2 is a very strong inhibitor of gastric acid and pepsin secretion induced by various secretory stimuli, particularly under basal conditions and in response to a meal. In view of prolonged inhibitory activity, 15-Me-PGE2 may have clinical potential in the treatment of peptic ulcer disease.

Gastric acid response to topical or intravenous histamine and topical H2-receptor blockade in dogs.

This study was undertaken to determine gastric acid response to histamine applied topically to the mucosal surface and to examine the local effect of ranitidine, a histamine H2-receptor antagonist, on the gastric acid response to histamine. Histamine applied to the Heidenhain pouch (HP) mucosa resulted in a slight and dose-dependent stimulation of acid secretion without affecting acid secretion from the main stomach. Ranitidine given into the HP caused dose-dependent inhibition of the HP response to topical or intravenous histamine without affecting the acid response of the main stomach and without any significant change in the serum ranitidine level. Ranitidine applied to the main stomach with the pylorus occluded inhibited histamineinduced acid secretion also without any increase in the serum ranitidine level. This inhibition was about 30% of that obtained with the same dose of ranitidine given into the stomach with the pylorus left open during the experiment. This study provides evidence that topical hsitamine is a weak stimulant of gastric secretion and that topical ranitidine is capable of local inhibition of the acid response to both topical or intravenous histamine.