Gastrin-like pentapeptide I.C.I. 50 123: a potent gastric stimulant in man

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.

Inhibition of pentagastrin-stimulated gastric acid secretion by intraileal administration of bile and elevation of plasma concentrations of gut glucagon-like immunoreactivity in anesthetized dogs

The effects of intraileal administration of bile on gastric acid secretion stimulated by a submaximal dose of intravenous pentagastrin infusion and on plasma concentrations of gut glucagon-like immunoreactivity (gut GLI) were studied in anesthetized dogs. Gastric acid secretion was measured for a 2-h period at 15-min intervals before and after intraluminal instillation of test solutions. 100 ml of canine bladder bile diluted to 10% in saline evoked a significant inhibition (20%) of gastric acid secretion. The inhibition of gastric acid secretion was accompanied by an elevation of plasma concentration of gut GLI, whereas saline instillation (in controls) caused no responses. Although the inhibition of gastric acid secretion and the elevation of plasma gut GLI are parallel phenomena, gut GLI can be reasonably postulated as one of the candidate mediators of bile-induced inhibition of gastric acid secretion, since its structurally related peptides, pancreatic glucagon, glicentin and oxyntomodulin have been reported as inhibitors of gastric acid secretion.

Absence of tachyphylaxis in gastric acid secretion during pentagastrin infusion

Tachyphylaxis to stimulation of gastric juice secretion during intravenous pentagastrin (PG) infusion has been reported in animal studies. We assessed the course of gastric response to PG 2 micrograms/kg/hr over eight hours in eight healthy subjects. Peak H+, pepsin, and volume secretions occurred during the second half hour of stimulation. Peak H+ output was 11.6 +/- 1.3 mmol/0.5 hr or 7.6 +/- 0.8% of the total eight-hour secretion. During subsequent half-hour collection intervals, there was no significant decline in response, and the average output was 10.3 +/- 0.4 mmol/0.5 hr (6.5 +/- 0.1%). Peak pepsin and volume secretions were respectively 10.0 +/- 1.4% (74.8 +/- 11.6 mg/0.5 hr) and 8.8 +/- 1.1% (146.3 +/- 17.4 mL/0.5 hr) of the total eight-hour secretion. Although there was a significant decline in pepsin and volume response subsequent to the peak output, the decline was not continuous, and pepsin and volume secretions were maintained, respectively, at 6.0 +/- 0.2% (46.1 +/- 2.5 mg/0.5 hr) and 6.2 +/- 0.1% (107.5 +/- 3.0 mL/0.5 hr) of the total eight-hour secretion. Our study did not demonstrate any tachyphylaxis in H+ response to continuous PG stimulation. This model appears to be a valid tool for the assessment of histamine-H2 antagonist effects on stimulated gastric juice secretion over 8 hours in humans.

Pentagastrin analogs containing alpha-aminooxy acids, I. Synthesis of analogs substituted at the N-terminus

Nine new pentagastrin analogs containing a free or protected alpha-aminooxy acid at the N-terminus were synthesized stepwise. Analogs containing leucyl, norleucyl, norvalyl, L- and D-2-aminodecanoyl residues instead of methionyl residue were also prepared. The peptides were synthesized by the active ester method with subsequent removal of the protecting groups. The purification of the end products was performed by crystallization or column chromatography on silica gel.

A small dose of somatostatin inhibits the pentagastrin stimulated gastric secretion of acid, pepsin and intrinsic factor in man

The effect of a small dose of somatostatin (0.05 mg/h) on the gastric secretion of acid, pepsin and Intrinsic Factor (IF) after stepwise increases in the dose of pentagastrin was examined in six healthy volunteers. The gastric secretion of acid, pepsin and IF in response to pentagastrin was significantly reduced by a continuous infusion of somatostatin. The pattern of inhibition indicates that somatostatin is a competitive inhibitor of pentagastrin in the stimulation of gastric secretion of both acid, pepsin and IF. This finding supports the hypothesis of a direct effect of somatostatin on the exocrine secretory cells of the stomach.

Effect of atropine on gastrin and gastric acid response to peptone meal

The action of intravenous atropine on meal-and pentagastrin-induced gastric acid secretion was studied in six duodenal ulcer patients.A test meal of 10% peptone solution adjusted to pH 5.0 was maintained in the stomach at at distention presure of 15 cm H(2)O, and a modification of the intragastric titration method of Fordtran and Walsh was used to measure gastric acid output by monitoring the rate at which a solution of 0.5 M sodium bicarbonate had to be added to keep the pH of the gastric content constant at the initial (pH 5.0) value. Serum gastrin concentrations were measured simultaneously by radioimmunoassy. The dose of 25 mug/kg-h atropine inhibited meal-induced acid secretion by about 70% and that evoked by pentagastrin by about 30%. The serum gastrin response to the test meal was not significantly altered by atropine. We conclude that atropine is a very strong inhibitor of meal-induced gastric acid secretion and does not significantly change serum gastrin response to feeding in duodenal ulcer patients when postprandial gastric acidity (pH 5.0) and intragastric pressure (15 cm H(2)O) are kept constant.

Effects of histamine acid phosphate and pentagastrin on gastric secretion in normal human subjects

Six normal subjects were tested with various doses of histamine acid phosphate (1, 10, 40, and 80 mug/kg/hr) and pentagastrin (0.15, 1.5, 6.0, and 12.0 mug/kg/hr), the different doses of the stimulants being administered by separate continuous intravenous infusions. In each sample of gastric juice, which was collected at 15-minute intervals, we estimated the concentrations of the H(+), Na(+), K(+), and Cl(-) and the concentration of pepsin. The drugs elicited equal maximal outputs of acid and pepsin. Pentagastrin was more potent than histamine in stimulating acid and pepsin secretion, and the rate of the responses was faster with pentagastrin than with histamine. Apart from this, however, the patterns of secretion of the various constituents of the gastric juice and the interrelationships between the concentrations of the electrolytes were identical with the two drugs. We therefore concluded that the actions of histamine acid phosphate and pentagastrin on human gastric secretion were identical.