Tissue Gastrin Concentrations Research Articles

Gastrin (g) and enterochromaffin: Like (ecl) cells in the stomach of portocaval-shunted rats: Radioimmunological, immunocytochemical and ultrastructural study

The aim of the study was to monitor the changes observed in the concentration of gastrin, as well as the morphological and ultrastructural properties of pyloric G and fundic ECL cells in rats with a portocaval shunt (PCS). Eight weeks after surgery, plasma and pyloric tissue gastrin concentrations were determined by radioimmunoassay. Sections from pyloric mucosa were immunostained for the identification of G cells, while oxyntic mucosa specimens were processed for Sevier-Munger detection of ECL cells. In addition, ultrastructural properties of G and ECL cells were determined by standard transmission electron microscopy. The results showed that the plasma gastrin levels were unchanged, while the pyloric gastrin concentrations were significantly increased in rats with PCS compared to the control animals (p<0.01). The morphometric analysis showed a significant increase in the cell density of antral G cells (p<0.05) and fundic ECL cells (p<0.01), as well as an increased number of these cells per mm2 of mucosa (p<0.01). In addition the ECL cell profile area was increased in rats with PCS. The predominance of very large vesicles and the reduction of normal cytoplasmic granules and vesicles was a prominent subcellular feature of the ECL. G-cells in PCS rats showed the presence of secretory granules of all types (electron-dense electron-lucent and electron-pale). The number of electron dense granules was elevated. These ultrastructural patterns are compatible with the functional activation of G and ECL cells. The present study suggests that PCS results in hyperplasia of G cells, as well as in both hyperplasia and hypertrophia of ECL cells. It is highly probable that the PCS enchances the sensitivity of the ECL cells to gastrin, thereby enabling them to respond to gastrin in an exaggerated manner.

Gastrin and antral G cells in course ofHelicobacter pylorieradication: Six months follow up study

To assess long-term effects of Helicobacter pylori (H pylori) eradication on antral G cell morphology and function in patients with and without duodenal ulcer (DU). Consecutive dyspeptic patients referred to the endoscopy entered the study. Out of 39 H pylori positive patients, 8 had DU (H pylori +DU) and 31 gastritis (H pylori +G). Control groups consisted of 11 uninfected dyspeptic patients (CG1) and 7 healthy volunteers (CG2). Basal plasma gastrin (PGL), antral tissue gastrin concentrations (ATGC), immunohistochemical and electron microscopic characteristics of G cells were determined, prior to and 6 mo after therapy. We demonstrated elevated PGL in infected patients compared to uninfected controls prior to therapy. Elevated PGL were registered in all H pylori+patients (H pylori +DU: 106.78+/-22.72 pg/mL, H pylori +G: 74.95+/-15.63, CG1: 68.59+/-17.97, CG2: 39.24+/-5.59 pg/mL, P<0.01). Successful eradication (e) therapy in H pylori+patients lead to significant decrease in PGL (H pylori+DU: 59.93+/-9.40 and H pylori +Ge: 42.36+/-10.28 pg/mL, P<0.001). ATGC at the beginning of the study were similar in infected and uninfected patients and eradication therapy lead to significant decrease in ATGC in H pylori +gastritis, but not in DU patients. In the H pylori +DU patients, the mean number of antral G cells was significantly lower in comparison with all other groups (P<0.01), but after successful eradication was close to normal values found in controls. By contrast, G cell number and volume density were significantly decreased (P<0.01) in H pylori +Ge group after successful eradication therapy (294+/-32 and 0.31+/-0.02, respectively), in comparison to values before eradication (416+/-40 and 0.48+/-0.09). No significant change of the G cell/total endocrine cell ratio was observed during the 6 mo of follow up in any of the groups. A reversible increase in G cell secretory function was seen in all infected individuals, demonstrated by a more prominent secretory apparatus. However, differences between DU and gastritis group were identified. H pylori infection induces antral G cell hyperfunction resulting in increased gastrin synthesis and secretion. After eradication therapy complete morphological and functional recovery is observed in patients with gastritis. In the DU patients some other factors unrelated to the H pylori infection influence antral G cell morphology and function.

Effects of Ostertagia ostertagi and omeprazole treatment on feed intake and gastrin-related responses in the calf

Infection with the bovine abomasal nematode, Ostertagia ostertagi, results in a loss of acid-secreting parietal cells and an increase in gastric pH. The effects of an experimental infection with Ostertagia and/or daily treatment with omeprazole (OMP) at 2 mg kg −1 bodyweight for four consecutive days (experiment days 24–27, inclusive) on voluntary feed intake, blood and tissue gastrin concentrations, abomasal G-cell numbers, gastric pH, and blood cholecystokinin (CCK) and pepsinogen concentrations were investigated in the calf. Ostertagia-infected calves demonstrated a significant drop in feed intake between days 24 and 27 post-infection (38%; P<0.001) and in G-cell numbers (42%; P<0.05) and significant increases in abomasal pH ( P<0.001), fundic mucosal weight (99%; P<0.01), and blood gastrin ( P<0.05) and pepsinogen ( P<0.0001). OMP treatment of worm-free animals resulted in a significant drop in intake between days 24 and 27 (30%; P<0.001) and in G-cell numbers (17%; P<0.05) and significant increases in abomasal pH ( P<0.01) and blood gastrin ( P<0.001). OMP treatment of Ostertagia-infected animals with an existing hypergastrinaemia had no effect on feed intake, abomasal pH, blood gastrin or pepsinogen or abomasal G-cell numbers. Blood CCK concentrations were also unaffected by either Ostertagia infection or OMP treatment. These data suggest that: (a) the depression in feed intake associated with OMP in worm-free calves was not due to a side effect of drug treatment; (b) inappetance in Ostertagia-infected animals is closely associated with the parasite-induced hypergastrinaemia; and (c) the elevation in abomasal pH was a major factor responsible for the elevated blood gastrin concentrations seen in parasitised and OMP-treated animals.

Gastrinaemia, Tissue Gastrin Concentration and G Cell Density in the Antral Mucosa of Swine With and Without Gastric Ulcer of the Pars Oesophagea

Gastric ulcer of the pars oesophagea (GUPO) of the stomach, which occurs spontaneously in swine, is of unknown aetiology. Because gastrin is a potent secretagogue linked to acid secretion, this study was designed to investigate, in pigs with or without GUPO, (1) basal and food-stimulated serum gastrin concentrations, (2) the concentration of tissue gastrin, and (3) gastrin-producing (G) cell density in the antral mucosa. Sixty-four pigs (32 with, and 32 without ulceration) were studied. Antral mucosa was obtained immediately after slaughter for assessment of G-cell number and tissue gastrin concentration. The presence or absence of GUPO was not significantly associated with either of the parameters measured.

Infection of sheep with adult and larval Ostertagia circumcincta: gastrin

Gastric endocrine cell populations and serum and tissue gastrin have been examined in sheep which were infected either intraruminally by tube with 150 000 Ostertagia circumcincta larvae followed by a trickle infection of 10 000 larvae thrice weekly for 8 weeks or by the transfer of 15 000 adult worms directly into the abomasum and killed 8 days later. Depletion of both antral gastrin and somatostatin was evident in both groups: tissue gastrin concentrations were reduced by 85% in the trickle infection and both G cells (gastrin-containing) and D cells (somatostatin-containing) were pale and fewer after adult worm transfer. The concurrent depletion of antral gastrin and somatostatin supports the contention that the hypergastrinaemia in parasitised sheep is largely secondary to the increase in abomasal pH. Although there was no change in the proportions of G34 and G17 in the tissues, there was an increase in the longer form of gastrin in the circulation of the larval-infected sheep, suggesting that there may be differential secretion of G17 and G34 which may be exaggerated as the rate of secretion increases. Although the fundic mucosa was thicker following trickle infection, there was no evidence of enterochromaffin-like cell hyperplasia in either infected group. It is suggested that hypergastrinaemia may be beneficial to the host, as it may allow the abomasum to regain the ability to acidify its contents during continued exposure to the parasites.

Effects of Ostertagia ostertagi on gastrin gene expression and gastrin‐related responses in the calf.

1. Infection with the bovine abomasal nematode Ostertagia ostertagi results in a loss of acid-secreting parietal cells and an increase in gastric pH. The effects of an experimental infection on gastrin mRNA expression, blood and tissue gastrin concentrations, the different molecular forms of gastrin in each, and pyloric mucosal chromogranin A-derived peptides were investigated in the calf. 2. An increase in blood gastrin concentrations in the infected group reached a peak by day 28 postinfection (635 pg ml-1; P < 0.01). Gel chromatography analysis of blood samples revealed that the hypergastrinaemia comprised largely gastrin-34 (G-34) in parasitized calves while gastrin-17 (G-17) predominated in control animals. 3. An 11-fold increase in gastrin mRNA expression was recorded in the parasitized animals which was accompanied by a 23.8% reduction in pyloric mucosal gastrin content and an apparent drop of 24.7% in the number of gastrin-producing G cells detected. There was no major change in the relative abundance of G-17 and G-34 in the pyloric mucosa of infected calves. No significant differences in the concentration of pyloric mucosal chromogranin A-derived peptides were recorded between infected and control groups. 4. These data suggest that the hypergastrinaemia seen in parasitized calves results largely from an increase in gastrin synthesis and that depletion of previously stored peptide makes virtually no contribution to elevated blood gastrin concentrations.

The regulation of gastrin secretion in the chicken

Chicken gastrin has a C-terminal sequence resembling mammalian cholecystokinin, but its biological properties resemble mammalian gastrin. The mechanisms controlling chicken gastrin release are poorly understood. We have investigated the factors which influence chicken gastrin secretion in vivo. Plasma gastrin concentration was decreased within 12 h of fasting, but tissue gastrin concentrations were not significantly changed even after 24 h of food deprivation. In birds fasted for 24 h and treated with the H +/K +-ATPase inhibitor, omeprazole, plasma gastrin concentration was greatly enhanced indicating the importance of acid inhibition of the gastrin cell. It is well established that amino acids (particularly aromatics like Phe and Trp) and peptides stimulate gastrin release in mammals. In chicken, however, Met, His and Arg were the strongest stimulant amongst the essential amino acids investigated. Of these three amino acids, Met rapidly stimulated gastrin release. The GRP antagonist M216140 did not suppress the Met-induced gastrin release, suggesting that Met did not stimulate GRP release. Aromatic amino acids did not strongly influence gastrin release. Medium chain triacylglycerol, which is rapidly hydrolyzed to fatty acids in the lumen, strongly stimulated gastrin secretion but long chain triacylglycerol had no effect. The data suggest that amino acids (Met, Arg and His) and fatty acids, but not triacylglycerol, are gastrin releasing factors in birds while acid inhibits secretion: there are therefore both similarities and differences between birds and mammals in the control of gastrin release.

Effects of carbamylcholine chloride on human antral gastrin mRNA levels.

The effects of the muscarinic receptor agonist, carbamylcholine chloride (carbachol), on gastrin release and gastrin mRNA levels in human antral mucosa (n = 15) were determined. During a-2-h incubation period, carbachol (10(-6)-10(-4) M) decreased gastrin mRNA levels to 71 +/- 8% (10(-6) M), 40 +/- 8% (10(-5) M), and 33 +/- 5% (10(-4) M) of control levels. Carbachol (10(-5) M) decreased intracellular gastrin (from 1634 +/- 103 to 1272 +/- 126 pg/mg tissue protein), while it increased gastrin release into the medium (from 609 +/- 48 to 918 +/- 68 pg/ml per mg tissue protein). After 6- and 9-h culture, carbachol gradually increased gastrin mRNA levels, by 96 +/- 12% and 126 +/- 23%, respectively. Atropine sulfate (10(-5) M) completely inhibited the carbachol-induced changes. Cycloheximide markedly decreased tissue gastrin concentration, but increased gastrin mRNA levels, whereas it had no effects on gastrin release. These findings suggested that carbachol may have a time-related biphasic action on human antral gastrin biosynthesis.

Effect of short-term administration of dexamethasone on canine antral gastrin gene expression.

The acute effect of corticosteroids on the release and biosynthesis of gastrin still remains unclear. We report the effect of short-term administration of dexamethasone on the antral gastrin gene expression and gastrin levels in 6 dogs, which were treated with dexamethasone (1.5 mg/kg, i.m. daily) for 3 days. One day after treatment, gastrin mRNA levels increased (152 +/- 14%), but serum and tissue gastrin showed no significant changes. With 2 and 3 days of dexamethasone treatment, gastrin mRNA (2 days: 163 +/- 28%, 3 days: 170 +/- 22%), serum gastrin (2 days: from 94 +/- 12 to 168 +/- 23 pg/ml, 3 days: to 180 +/- 16 pg/ml) and tissue gastrin concentration (2 days: from 480 +/- 32 to 664 +/- 31 pg/mg tissue protein, 3 days: to 708 +/- 45 pg/mg tissue protein) significantly increased. However, gastrin mRNA levels were not increased even after 1 day culture of canine antral tissue with dexamethasone in vitro. These findings suggest that short-term administration of corticosteroid may increase the canine gastrin gene expression in vivo by an unknown pathway.

The secretory kinetics of the G cell in omeprazole-treated rats

Prolonged achlorhydria leads to hypergastrinemia which must be matched by increased gastrin production. The extent to which the balance between synthesis and storage or secretion is shifted in achlorhydria remains uncertain. In the present study, rats were treated for 14 days with the hydrogen-potassium-stimulated ATPase inhibitor omeprazole, and the effects on plasma and tissue gastrin concentrations and on the abundance of gastrin messenger RNA were examined. To calculate the fractional release rates of gastrin, the metabolic clearance rate of synthetic unsulfated rat heptadeca peptide gastrin in anesthetized rats was also measured. Treatment with omeprazole for 14 days led to a profound hypergastrinemia, a twofold increase in antral gastrin stores, and a tenfold increase in messenger RNA. Calculations based on the metabolic clearance rate for rat heptadecapeptide gastrin suggested that in control rats, about 0.08% of stored gastrin was released per minute compared with about 0.4% in omeprazole-treated rats. No evidence was observed to suggest that changes in the efficiency of conversion of Gly-extended gastrins to amidated peptides were of any significance in accounting for the increased production of amidated gastrin. The increased gastrin synthesis in achlorhydria is therefore attributable to increased messenger RNA levels; most of the increase in gastrin production is directly secreted as changes in the stores of gastrin appear to be of lesser importance.

The Secretory Kinetics of the G Cell in Omeprazole-Treated Rats

Prolonged achlorhydria leads to hypergastrinemia which must be matched by increased gastrin production. The extent to which the balance between synthesis and storage or secretion is shifted in achlorhydria remains uncertain. In the present study, rats were treated for 14 days with the hydrogen-potassium-stimulated ATPase inhibitor omeprazole, and the effects on plasma and tissue gastrin concentrations and on the abundance of gastrin messenger RNA were examined. To calculate the fractional release rates of gastrin, the metabolic clearance rate of synthetic unsulfated rat heptadeca peptide gastrin in anesthetized rats was also measured. Treatment with omeprazole for 14 days led to a profound hypergastrinemia, a twofold increase in antral gastrin stores, and a tenfold increase in messenger RNA. Calculations based on the metabolic clearance rate for rat heptadecapeptide gastrin suggested that in control rats, about 0.08% of stored gastrin was released per minute compared with about 0.4% in omeprazole-treated rats. No evidence was observed to suggest that changes in the efficiency of conversion of Gly-extended gastrins to amidated peptides were of any significance in accounting for the increased production of amidated gastrin. The increased gastrin synthesis in achlorhydria is therefore attributable to increased messenger RNA levels; most of the increase in gastrin production is directly secreted as changes in the stores of gastrin appear to be of lesser importance.

Reversal by omeprazole of the depression of gastrin cell function by fasting in the rat.

1. Gastrin (G)-cell function is controlled by gastric acid, which has inhibitory effects, and food in the gastric lumen, which has stimulatory effects. We have examined the role of acid in mediating the depression of G-cell function that occurs in fasting in the rat. 2. Rats were fasted for 48 h, and received either the H(+)-K(+)-ATPase inhibitor omeprazole, to reduce acid secretion, or vehicle. Basal acid secretion was not significantly different after fasting for 24 or 48 h. Fasted rats which received omeprazole were achlorhydric. 3. In rats treated with vehicle and fasted for 48 h, plasma and tissue gastrin concentrations were significantly depressed. The fall in both parameters suggests an inhibition of gastrin synthesis and consistent with this a decrease was observed in tissue gastrin mRNA abundance and in phosphorylation of progastrin-derived peptides. 4. In fasted rats treated with omeprazole, tissue gastrin concentrations were not significantly different from those of rats fed ad libitum, but plasma gastrin concentrations were significantly higher than in rats fed ad libitum. Gastrin mRNA abundance and the phosphorylation of progastrin-derived peptides in omeprazole-treated rats was not significantly different from rats fed ad libitum. 5. The data suggest that the depression of G-cell function which occurs in fasted rats can be attributed to the inhibitory action of intraluminal acid on the G-cell. Gastric acid appears to regulate several different aspects of G-cell function, including gastrin synthesis, post-translational processing and secretion.

Modulation of posttranslational processing of gastrin precursor in dogs

The precursor of the acid-stimulating hormone gastrin is processed in pyloric antral gastrin cells by steps involving sulfation, phosphorylation, cleavage, and amidation. We describe here changes in posttranslational processing in dogs with a surgically excluded antrum; in the preparation we used there was an intact pylorus but antral mucosa was excluded from the normal influence of the luminal contents. Three to five months after the operation, basal plasma gastrin increased from 30.1 +/- 4.0 to 66.1 +/- 16.1 pmol/l, and concentrations of gastrin in the excluded mucosa were 9.23 +/- 1.75 compared with 3.2 +/- 0.56 nmol/g in control antral mucosa. Calculations based on the metabolic clearance rate and plasma and tissue gastrin concentrations suggest two-fold lower fractional release rates from the excluded G-cells compared with normal G-cells. Radioimmunoassay of tissue extracts using antisera specific for the extreme COOH-terminus of progastrin, for glycine-extended G-17, and for the COOH-terminus of G-17, combined with gel filtration and ion exchange chromatography, indicated normal endopeptidase cleavage of progastrin. However there was significantly reduced phosphorylation of the COOH-terminal tryptic fragment of progastrin, and there was also decreased conversion of Gly-extended intermediates to the biologically active COOH-terminally amidated forms of gastrin. Thus, in spite of hypergastrinaemia, the excluded antral mucosa showed evidence of decreased secretory rates associated with decreased progastrin phosphorylation and amidating enzyme activity. The results suggest that contact of antral mucosa with the luminal contents is able to modulate the posttranslational processing of progastrin and so determine the production of biologically active hormone.

Role of the proximal duodenum in gastrin regulation following antrectomy.

Antrectomy is accepted as the most effective surgical treatment of recurrent duodenal ulcer after complete vagotomy. Although antrectomy is aimed at reducing serum gastrin levels, both human and experimental reports seem to indicate that gastrin concentrations may be unchanged following this operation. The probable source of gastrin has been considered to be the proximal third of the duodenum, since at this level increased tissue gastrin concentrations were found after antrectomy. The present study was carried out in order to gain insight into the mechanism by which the duodenum may compensate for the removal of the antrum. Forty white rats were randomly divided into two equal groups and underwent antrectomy with gastroduodenostomy or simple laparotomy. Three to four months after surgery, serum gastrin determinations were carried out by radioimmunoassay both in fasted and freely fed rats. The duodenum was then removed and its proximal third was used for G cell counts (immunoperoxidase method) and for assessment of G cell cytoplasmic granule distribution (electron-microscopic examination). Antrectomy significantly increased fasting serum gastrin levels (p less than 0.01), while it completely abolished the gastrin response to food ingestion (p less than 0.001). In antrectomized rats, the duodenal G cell number was significantly higher than in control rats (p less than 0.001), whilst the G cell cytoplasmic granule number remained unchanged. In conclusion, the present study indicates that in the rat the proximal duodenum increases its content of tissue gastrin following antrectomy mainly by enhancing the regional G cell density.

Increased antral G-cell number and gastrin content in dogs after massive small bowel resection.

The effects of massive small-bowel resection on antral gastrin tissue concentration and G-cell number have been investigated in the dog. Tissue gastrin concentrations increased significantly after resection from 16.8 +/- 2.6 ng/mg wet weight to 30.3 +/- 3.2 ng. Immunoreactive gastrin cell number also increased from 29.8 +/- 2.5 cell/mm2 to 43.1 +/- 3.0 cells/mm2. Immunocytochemistry demonstrated that the hyperplastic gastrin cells were found in small groups, with the majority of the immunoreactivity located at the luminal pole of the cells. This finding, linked to hypogastrinemia in the dogs after massive small bowel resection, suggests that some of the hyperplastic G cells may have an exocrine rather than endocrine function.

Ontogeny of tissue and serum gastrin concentrations in fetal and neonatal sheep.

We investigated the perinatal ontogenic changes in ovine serum and tissue gastrin concentration. Fetal and maternal serum gastrin levels in serums obtained from indwelling catheters in the fetal and maternal circulations and tissue gastrin levels were assessed by radioimmunoassay and immunohistochemistry. Fetal serum gastrin concentration was undetectable until the 107th day of gestation and significantly increased to levels surpassing maternal values. Neonatal serum hormone concentration continued to rise, reaching a peak during the 4th postnatal wk and decreasing after the 4th wk coincident with weaning. Maternal serum gastrin concentration did not vary during pregnancy and did not correlate with fetal serum gastrin levels. Fetal abomasal and duodenal gastrin concentrations and abomasal G-cell number increased in parallel with the developmental alterations in fetal serum hormone levels during gestation. The developmental increase in abomasal gastrin concentration was not associated with a shift in the molecular form of the hormone. These findings support the hypothesis that circulating gastrin in the fetus is of fetal origin.

Alterations in serum and antral gastrin levels in genetically diabetic mice

Many gastrointestinal structural and functional properties are known to be altered in diabetes. In this study, we investigated whether serum and tissue gastrin levels are abnormally altered in a strain of genetically diabetic mice (C57BL/KSJ). Both serum and antral gastrin concentration were found to be significantly increased 3.4- and 2-fold above normal values in diabetic mice fed ad libitum. The increase in tissue gastrin concentration is most probably due to an increase in both cellular gastrin content and G-cell number, since the latter property is increased 130% in diabetic animals. Pair feeding studies demonstrated that diabetes associated hyperphagia is not a major factor in inducing these endocrine changes, since antral and serum gastrin are still significantly elevated above normal in diabetic animals fed a restricted diet. G-cell number, however, is not significantly increased above normal values in pair fed diabetic mice. The peak serum gastrin concentration after a meal and the duration of postprandial hypergastrinemia are also significantly increased above normal in diabetic animals. Gel filtration chromatography studies indicate that the antral mucosae of normal and diabetic mice have identical molecular forms of the hormone. It is therefore concluded that antral and serum gastrin concentration are increased in genetically diabetic mice due to both dietary alterations and other, as yet undefined, factors specific for the disease, and that the resultant hypergastrinemia may contribute to some of the gastrointestinal alterations seen in diabetes.

Serum and Tissue Gastrin Concentrations in Patients with Carcinoma of the Stomach

Fasting serum gastrin concentrations and gastric acid secretory rates were examined in 22 patients with carcinoma of the stomach. The mean fasting serum gastrin concentration for the patients with carcinoma of the stomach (344 ± 52 pg per ml) substantially and significantly exceeded that for a control population of patients without recognized gastrointestinal disease (P