Sequential somatostatin and gastrin releases in response to secretin in rat in vivo.

Secretin in known to inhibit gastric acid secretion. Exogenous secretin has also been shown to have a biphasic effect on acid secretion, being stimulatory then inhibitory. To explain this effect, we studied the timing of gastrin, somatostatin, and HCl releases in the gastric lumen in response to an i.v. bolus of secretin (360 pmol) or saline in conscious rats provided with a chronic double gastric fistula and having had or not antrectomy. After secretin but not saline, an immediate and transient increase in acid and gastrin secretions was first observed. After a 4 min lag, a dramatic increase in somatostatin secretion was then observed, together with a 90 percent inhibition of acid secretion and a return of gastrin release to basal level. Twenty min after secretin administration, a rebound increase in acid and gastrin outputs occurred, whereas somatostatin output returned to basal level. The secretin-induced somatostatin release was higher in rats with antrectomy than in those without antrectomy suggesting that the observed somatostatin output mostly originated from the fundus. This present study suggests that a bolus of secretin induced a gastrin release and thus could stimulate acid secretion. These pharmacological findings could provide an explanation for the so-called paradoxical secretin-induced stimulation of gastrin secretion in particular conditions.

[Tri-annual rhythm of basal acid secretion and secretion stimulated by pentagastrin in duodenal ulcer]. / Rythmes tri-annuels de la sécrétion acide basale et stimulée par la pentagastrine dans l'ulcère duodénal.

Duodenal ulcer is a recurrent disease with seasonal periodicity for pain and complications such as hemorrhage and perforation. Ulcer craters or symptoms seem to occur preferentially in early spring and autumn. Since acid secretion is one of the pathogenetic factors of the disease, we analyzed retrospectively basal and maximal (pentagastrin) acid secretion data obtained in 341 consecutive patients according to the month in which they were obtained. The patients were classified according to the activity of their ulcer (active, non active) and to the level of the peak acid secretion (hypersecretors, normosecretors). Basal acid concentration and output, and peak acid output were, both overall and month by month, higher in patients with active duodenal ulcer disease than in those who were non active, and in hypersecretors than in normosecretors. For all 341 patients as well as for normosecretors and non active ulcer patients, a triannual rhythm was detected for stimulated acid concentration and peak acid output. The highest values were noted in February, June, and October (period: 4 months). The amplitude of these rhythms was 3 to 4 percent, with differences between highest and lowest values of 30.4 mmol/l for concentration and 17.1 mmol/h for peak acid output. These rhythms for acid secretion during the year may contribute to the periodicity of duodenal ulcer events and should be analyzed in association with other factors which could be implied in ulcerogenesis. Moreover, this seasonal periodicity of acid secretion in duodenal ulcer should be taken into account in all therapeutic trials in which acid secretion is analyzed.

Pancreatic polypeptide response to insulin in duodenal ulcer. Different levels in accordance with ulcer activity and its response to treatment.

Pancreatic polypeptide is said to be a marker of vagal tone in duodenal ulcer. To determine whether pancreatic polypeptide levels are related to the course of duodenal ulcer, we studied acid and pancreatic polypeptide responses to insulin in 80 patients with duodenal ulcer disease: 40 with unoperated duodenal ulcer and 40 with proximal vagotomy. Data were analysed in accordance with the presence of an ulcer (active disease) and, when present, in accordance with the ulcer healing on medical treatment (cimetidine, 1 g/day for 4 weeks). In both groups acid and pancreatic polypeptide responses to hypoglycaemia were slightly correlated (r = 0.38) (p less than 0.05). The basal pancreatic polypeptide level was higher in patients with active disease than in those with inactive disease, who had a basal level similar to that of normal subjects of the same age range. Like the insulin-stimulated acid secretion, the pancreatic polypeptide response to insulin hypoglycaemia was higher in patients with active disease than in those with inactive disease (p less than 0.05): 26.1 +/- 3.9 versus 20.1 +/- 4 nmol/l/120 min, respectively, in unoperated patients and 34.8 +/- 2.2 versus 24.3 +/- 2.5 nmol/l/120 min, respectively, after proximal vagotomy. In active disease the pancreatic polypeptide response to insulin hypoglycaemia was higher in subjects whose ulcer did not heal further after cimetidine therapy than in those whose ulcer did. These data suggest that the pancreatic polypeptide response to insulin is an indicator of duodenal ulcer activity and is related to the treatment efficacy. These relationships are partly mediated by increased vagal tone.

Persistence of circadian rhythms in gastric acid, gastrin, and pancreatic polypeptide secretions despite loss of cortisol and body temperature rhythms in man under stress.

During organic stress, severe dysfunctions of fundamental biological phenomena, such as modification of vagal tone, have been described. These dysfunctions could induce changes in the rhythm of acid secretion and/or its hormonal control. We therefore analyzed the effects of acute respiratory failure on the 24 h variations in intragastric pH, serum gastrin, and pancreatic polypeptide levels, taken as a marker of vagal tone. Body temperature and plasma cortisol circadian rhythms were used as marker rhythms. Twelve patients with chronic obstructive pulmonary disease complicated with acute respiratory failure were studied before and during continuous enteral nutrition; half of the patients received ranitidine, a H2 blocker. During the 3 days of the study, intragastric pH was below 2.5 for only one third of the time. No difference was observed between the placebo and the ranitidine groups. Plasma pancreatic polypeptide was within normal ranges despite increased cortisol levels. Gastrin levels reflected changes in intragastric pH over the 24 h time frame and were noted to increase during ranitidine and enteral nutrition. Despite the loss of cortisol and body temperature circadian rhythmicity all throughout the study, circadian rhythms were maintained or restored during the different therapeutic regimens for intragastric pH, serum gastrin, and pancreatic polypeptide levels. Moreover, an ultradian rhythm for gastrin before any treatment, a circadian rhythm for intragastric pH on enteral nutrition, a circadian rhythm for intragastric pH, plasma gastrin and plasma pancreatic polypeptide on ranitidine regimen were observed. Thus during acute respiratory failure, certain physiological circadian rhythms persisted despite the disappearance of "marker" rhythms. Furthermore, these rhythms for digestive secretions could be pharmacologically restored.

Small bowel and plasma gastrin rhythms in cats.

The purpose of this experiment was to study the possible role of the gastric antrum and small bowel in the rhythm(s) of plasma gastrin. The cat was used as the laboratory animal. Three groups of cats were provided with a gastric fistula for the study of gastric acid and plasma gastrin rhythms. The first group (N = 7) served as controls. A second group (N = 3) was antrectomized and later subjected to a 80% small bowel resection. Gastric acid secretions were collected every 30 min from 0800 to 2400. Blood samples for determination of gastrin were drawn every 2 hr from 0800 to 2400. In control animals a circadian (i.e. approximately 24 hr) and 3 ultradian (i.e. less than 24 hr) rhythms were detected for acid output. In the antrectomized cats, circadian and ultradian rhythms were documented. After small bowel resection circadian and ultradian rhythms in gastric acid secretion were observed. For plasma gastrin, circadian and ultradian rhythms were found in the control cats. In the antrectomized cats no rhythms were observed. After small bowel resection an ultradian rhythm reappeared in these antrectomized cats. Removal of the antrum in the cat induces disappearance of circadian and ultradian rhythms of plasma gastrin but fails to modify the acid rhythms. Small bowel resection results in the reappearance of an ultradian rhythm for plasma gastrin and a shift in acrophase for the circadian rhythm in acid secretion.

[Histologic aspect of the human gastric mucosa: relation to gastrin and somatostatin cells and the intraluminal secretion of these peptides]. / Aspect histologique de la muqueuse gastrique humaine: relations avec les cellules à gastrine et à somatostatine et la sécrétion intraluminale de ces peptides.

Fifty-eight subjects including controls, patients with duodenal ulcer, non-operated or treated with a superselective vagotomy underwent endoscopic fundic and antral biopsies. Histologic classification of the two mucosae was performed. We examined the relationship between the histologic grade of gastritis in the two mucosae, then between the histologic aspect of the antral mucosa and antral gastrin-and somatostatin-cell densities, the basal intraluminal secretion of gastrin and somatostatin. There was a significant correlation between the histologic aspect of fundic or antral mucosa and the age of patients, except in the case of vagotomized patients. Fundic and antral histologic patterns were also correlated in each patient, except for vagotomized. Gastrin and somatostatin cell densities showed no variation in function of the degree of inflammation of non atrophic gastritis. These cell densities showed a tendency to decrease in atrophic gastritis, especially when intestinal metaplasia was present. Intraluminal gastrin secretion was increased in patients with mild atrophic gastritis (p less than 0.05 to p less than 0.02) in comparison with those whose histology was roughly normal. It was also increased in severe atrophic gastritis. The highest intraluminal secretion of somatostatin was observed in patients with mild atrophic gastritis while this secretion fell noticeably in those showing severe atrophic gastritis, as compared to the other groups. This work seems to suggest a relationship between intraluminal peptides and the evolution of gastritis. While results are still preliminary, they do not indicate that these peptides, thus released, play any pathophysiologic role.

Intragastric pH profile during acute respiratory failure in patients with chronic obstructive pulmonary disease. Effect of ranitidine and enteral feeding.

The ability of H2 receptor antagonists and continuous enteral alimentation to maintain high intragastric pH in patients with chronic obstructive pulmonary disease (COPD) requiring mechanical ventilation was evaluated by continuously monitoring intragastric pH prior to and following sequential addition of ranitidine or continuous enteral alimentation (or both) to their therapeutic regimen. Prior to therapy, intragastric pH was less than 4.0 for 75 +/- 10 percent of the time, but never less than 1.0. Nevertheless, this moderate gastric acidity was associated with evidence of mucosal injury. Ranitidine failed to continuously maintain a high intragastric pH (pH less than 4.0 for 35 +/- 11 percent of the time; p greater than 0.2 compared to patients treated with placebo). Following administration of continuous enteral alimentation, intragastric pH fell, and ranitidine therapy only partially blocked this increase in gastric acidity induced by continuous enteral alimentation. We conclude that without treatment, patients with COPD who have acute respiratory failure may develop gastric mucosal injury despite the presence of only moderate intragastric acidity; however, ranitidine and continuous enteral alimentation are not effective in maintaining a high intragastric pH.

Sensitivity, specificity and predictive values of the secretin infusion test in the diagnosis of gastrinoma.

From 1974 to 1981, 55 patients, 18 with Zollinger-Ellison syndrome (ZES) histologically confirmed and 37 patients with duodenal ulcer (DU) without pylorostenosis were followed for a minimal period of 5 years. The diagnostic values of a) basal acid output (BAO mEq/h); b) 60 min acid output after secretin infusion, 3 CU-GIH/kg, (MAO-SE mEq/h); c) basal serum gastrin (BSG pg/ml: mean of 4 gastrin determinations) and d) serum gastrin after secretin (SG-SE pg/ml: mean of 4 gastrin determinations during secretin infusion) were calculated. Cut off point values of 100 p. 100 specificity (i. e. no DU patient reached these values) with a positive predictive value of 100 p. 100 (i. e. probability for gastrinoma when this cut off point was attained) were BAO greater than 26 mEq/h, MAO-SE greater than 18 mEq/h, BSG greater than 221 pg/ml, SG-SE greater than 186 pg/ml. The sensitivities of these parameters (i. e. percent of ZES which reached the given cut off point) were respectively (p. 100): 39, 78, 72 and 94. Ranking these parameters according to their own discriminative value expressed by R2 (square correlation coefficient) gave SG-SE, R2 = 0.559; BSG, R2 = 0.508; MAO-SE, R2 = 0.456; BAO, R2 = 0.414. The most discriminative association of 2 variables was SG-SE and MAO-SE (R2 = 0.650). Association of SG-SE, MAO-SE and BAO or BSG (or BAO and BSG) did not increase significantly the discrimination between ZES and DU (R2 = 0.672).

Antral gastrin- and somatostatin-producing cells and intraluminal peptide secretion in normal subjects and duodenal ulcer patients with and without vagotomy.

The behaviour of gastrin (G) cells and somatostatin (D) cells in endoscopic antral biopsies and that of intraluminal gastrin (ILG) and somatostatin (ILS) release in the gastric juice were investigated in three groups of patients: control subjects, duodenal ulcer (DU) patients and DU patients treated by a superselective vagotomy (SSV). G and D cell densities were correlated in the three groups of subjects. The G/D cell ratio was significantly increased in SSV patients (P less than 0.001) as compared to control and DU patients. No correlation was found between gastrin or somatostatin cell densities and basal intraluminal levels of the two peptides. ILG output was significantly higher in DU patients than in control or SSV patients (P less than 0.001). ILS output was also higher in DU patients than in controls (P less than 0.001) and in SSV patients (P less than 0.05). It was also significantly augmented in SSV (P less than 0.001) as compared to control patients. ILG and ILS concentrations were only correlated in controls. Within each of the three groups of subjects, ILG and ILS release varied in function of the gastric juice pH. Our results emphasize the necessity to consider the intragastric pH as well as the physiological or pathological state to study intraluminal peptides in man.

Mucus, gastrin and somatostatin cells in cultured rat antral mucosa: immunofluorescence, ultrastructural and radioimmunological studies.

Cells were isolated from the gastric antrum of newborn rats (7 and 10 days old) with the intent of studying mucus, gastrin (G), and somatostatin (D) cells. These cells were maintained in culture for 20 days. Their secretory properties were studied in vitro by cytochemical, immunocytochemical and radioimmunological methods. In vitro, mucus cells as well as G and D cells synthesized their secretory products intensely for the first 48 h, but beyond this point, their activity decreased. Mucus cells had a high rate of multiplication and formed sheets of epithelial cells in vitro. Their PAS-positive secretions were synthesized up until the 7th day of culture. During the first 3 days of culture, gastrin cells secreted detectable amounts of the hormone in the culture medium, but afterwards their secretion decreased. Somatostatin cells remained active until at least the 7th day of culture. They displayed long cytoplasmic processes which may serve as a means of communication with neighboring cells. Using ultrastructural techniques, mucus and endocrine cells were found to persist in culture. From a morphological point of view, they appeared similar to the cells found in the original antral tissue and this is an argument for the persistence of the secretory properties in cultivated cells. This experimental model appears to be reproducible and may be useful in the study of secretions of somatostatin, gastrin and mucus in the gastric antrum of the rat.

Growth hormone-releasing factor (somatocrinin) stimulates epithelial cell proliferation in the rat digestive tract.

The possible influence of growth hormone-releasing factor (GHRF) on epithelial cell proliferation in the digestive tract was investigated. Fasted young rats received five hourly subcutaneous injections of either GHRF or saline. They were killed 6, 12, or 18 h after the initial injection and 45 min after [3H]thymidine pulse labeling. At the time of death, blood was taken to determine circulating growth hormone and gastrin levels. After radioautography, DNA synthetic and mitotic activities were estimated in the fundic, antral, duodenal, jejunal, and colonic mucosae. Growth hormone-releasing factor significantly increased labeling indices 6, 12, and 18 h after the initial injection in fundic mucosa, and 6 and 18 h after injection in antral and duodenal mucosae. Furthermore, GHRF significantly increased mitotic indices at 12 h in fundic mucosa and at 12 and 18 h in jejunal mucosa. No effect was seen in the colon. At the three checkpoint times, circulating growth hormone showed no change, but plasma gastrin was increased in the rats treated with GHRF as compared with controls. However, whether the reported stimulatory effect of the GHRF on target cells is direct or indirect remains to be determined.

Growth hormone releasing hormone stimulates the release of gastrin in rat.

The inhibitory effect of somatostatin on gastrin release is well known. Could the growth hormone releasing hormone (GHRH), an antagonist of somatostatin on growth hormone (GH) release, have a gastrin-releasing effect on gastrin? To answer this question, two types of experiments were conducted: (1) The study of the effect of GHRH on gastrin in rats, which showed a significant and dose related release for the three doses studied: 0.12, 0.6 and 3.0 micrograms/rat. (2) The study on the recurrence of this gastrin releasing effect which has been found to be significant (1 to 5 injections at 1 hour intervals). Our data suggest that GHRH is an hypothalamic releasing factor for gastrin release. Accordingly, gastrin may mediate the observed proliferative effect of GHRH in the upper digestive tract.

[Consequences of antral and duodenal acidification on acid secretion, gastrin response and gastric emptying in duodenal ulcer patients and normal subjects]. / Conséquences de l'acidification antrale et duodénale sur le débit acide, la réponse gastrinique et la vidange gastrique chez l'ulcéreux duodénal et le sujet normal.

The present study intended to investigate the effect of antroduodenal acidification on gastric acid secretion and emptying, gastrin and somatostatin release in response to food in healthy subjects as well as in duodenal ulcer patients. Ten duodenal ulcer patients and 9 normal controls were studied twice: the same 400 ml liquid protein meal (proteins: 10 g) was introduced into the stomach; then intragastric pH was either maintained at pH 4.5 or allowed to decrease in response to the meal. Acid secretion was calculated using the intragastric titration method (for which the intragastric pH is fixed at pH 4.5) and using the serial dilution indicator method (which allows antral acidification) respectively. Gastric emptying was estimated according to: a) iterative measurements of intragastric meal residual volume; b) volume passing through the pylorus. These two tests were performed in a random order and during each, plasma gastrin and somatostatin responses to the meal were determined. In healthy subjects, antral acidification following the meal was associated with a significantly lower acid secretion (17.3 +/- 0.9 mmol/h; m +/- SEM) than when the pH was maintained at pH 4.5 (20.2 +/- 1.3; p less than 0.05). Moreover, gastric emptying was slower when the pH was allowed to decrease (t 1/2: 26.2 +/- 1.4 min) than when the pH was constant (t 1/2: 20.5 +/- 2.2 min; p less than 0.05). By contrast, in the duodenal ulcer group, neither acid output nor gastric emptying were significantly different in the two situations.(ABSTRACT TRUNCATED AT 250 WORDS)

A comparative evaluation of secretin bolus and secretin infusion as secretin provocation tests in the Zollinger-Ellison syndrome.

GIH secretin bolus (2 CU/kg) and infusion (3 CU/kg/h) have been randomly compared in 9 ZES patients and 10 age-matched DU patients. Serum gastrin and gastric acid variations were studied before and after either mode of secretin administration in the same individuals. Plasma secretin modifications were monitored in parallel. In both ZES and DU, secretin bolus and infusion induced similar gastrin responses (maximal changes and integrated responses). However, secretin infusion had a greater effect on acid output than bolus: larger inhibition in DU and larger increase in ZES. The additive diagnostic value of gastric acid secretion study during a secretin provocation test, as already reported, favors the use of 3 CU/kg/h secretin infusion over that of 2 CU/kg secretin bolus.

Antramine (antral histamine) antagonizes somatostatin inhibition on endogenous gastrin-induced gastric secretion. A new hypothesis for the role of histamine in gastric secretion regulation.

The effects of antramine, an antral histamine (AH), and of synthetic histamine (SH) on acid, pepsin, and gastrin responses to meals alone or in combination with somatostatin were studied in dogs equipped with a Heidenhain pouch. Food-induced acid secretion was potentiated by AH and only slightly increased by SH. Pepsin secretion was increased by AH and decreased by SH. Both AH and SH suppressed the inhibitory activity of somatostatin on food-induced secretion. AH potentiated gastrin response to feeding but decreased it when somatostatin was added to the meal. Since acid secretion was unrelated to gastrin response, it would appear that the secretory effects of AH involve a direct action on secreting cells, itself based on the suppression of somatostatin inhibition. Gastric secretion is probably related to gastrin efficacy on secreting cells, which would result from the antagonistic effects of somatostatin and AH. These data suggest an alternative hypothesis concerning the role of histamine in the control of gastric secretion.

Detection of tyrosine-specific protein kinases with gastrin as exogenous substrate.

Gastrin was recently shown to be phosphorylated on its single tyrosine by the epidermal growth factor (EGF)-stimulated tyrosine protein kinase (TPK). The TPK previously detected in the murine lymphoma (LSTRA) induced by the Moloney murine leukemia virus phosphorylates gastrin, the apparent Km is 65 microM and the maximum rate 1900 pmol/min per mg; the kinase is more efficient with MnCl2 than with MgCl2, is stimulated by NaVO3 and inhibited by ZnCl2. Gastrin phosphorylation is observed only when a TPK is expressed by the cell: extracts of fibroblasts infected with a temperature-sensitive mutant of the Rous sarcoma virus had no gastrin kinase activity when grown at the non-permissive temperature whereas cells grown at the permissive temperature were transformed and disclosed a clear gastrin kinase activity. Gastrin kinases were detected in various transformed cells: human lymphomas, K562 cells, cells from a patient with acute proliferative leukemia, and normal cells: human T and B lymphocytes.

[Release of pancreatic polypeptide in response to the intragastric administration of a meal is not different in duodenal ulcer patients and normal subjects]. / La libération de polypeptide pancréatique en réponse à l-administration intra-gastrique d'un repas n'est pas différente chez des ulcéreux duodénaux et des sujets normaux.

The high basal and meal-induced acid secretions in duodenal ulcer patients has led to the concept that vagal hyperactivity is a common factor in the pathogenesis of peptic ulcer. For these reasons, since pancreatic polypeptide secretion is known to be under vagal control, we studied the pancreatic polypeptide release after intragastric administration of two protein meals (10 and 20 g protein in 400 ml) in 18 duodenal ulcer patients and in 17 normal subjects. After a 10 g protein meal was administered, gastric pH was either maintained at pH 4.5 or allowed to decrease. The 20 g protein meal induced a higher pancreatic polypeptide release than did the 10 g protein meal (p less than 0.05): the integrated pancreatic polypeptide responses were 1.07 +/- 0.5 and 3.21 +/- 0.58 nmol/l/60 min respectively in the duodenal ulcer group and 0.46 +/- 0.21 and 2.67 +/- 0.69 nmol/l/60 min respectively in the control group. On the other hand, the responses to the two protein meals in duodenal ulcer patients were not different from those obtained in normal subjects, despite the higher meal-induced acid secretions in the duodenal ulcer group. pancreatic polypeptide increase was not larger when gastric pH was fixed than when it was allowed to decrease, 0.56 +/- 0.21 and 1.7 +/- 0.63 nmol/l/60 min respectively in normal subjects and 1.07 +/- 0.5 and 1.07 +/- 0.49 nmol/l/60 min respectively in duodenal ulcer patients.(ABSTRACT TRUNCATED AT 250 WORDS)