Complete sulfation of jejunal gastrin in the human fetus

The degree of tyrosine-O-sulfation and the ratio between large (gastrin-34 and component I) and small (gastrin-17 and -14) molecular forms of gastrin were studied in extracts of human fetal (n = 14) and adult (n = 9) antrum, duodenum, jejunum and pancreas. Boiled water extracts were applied to gel- and ion-exchange chromatography before and after treatment with trypsin and arylsulfatase. The fractions were monitored with sequence-specific radioimmunoassays that distinguish sulfated from non-sulfated gastrins. In antrum and duodenum about half the gastrins were sulfated at all stages of development. In the fetal jejunum gastrin occurred in sulfated form only while in the adult 72% (range, 64–88%) of the jejunal gastrins were sulfated. The larger molecular forms of gastrin predominated in the fetal compared with the adult antrum. In duodenum and jejunum, however, the ratio between small and large forms was the same in fetus and adult. Gastrin was undetectable in both fetal and adult pancreas. The results show that the degree of sulfation of gastrin varies substantially in the different parts of the gut at different stages of development. The differences may have functional significance, since sulfation increases the pancreozyminic and cholecystokinetic potency of gastrin.     

Biologically active gastrin/CCK-related peptides in the stomach of a reptile, Crocodylus niloticus; Identified and characterized by immunochemical methods

We have used immunochemical, chromatographic, and bioassay techniques to characterize peptides related to gastrin and CCK, from the stomach of the reptile Crocodylus niloticus. By immunocytochemistry gastrin/CCK-like peptides were localized in specific mucosal cells of the pylorus and in the duodenum. Boiling water extracts of pyloric antrum cross reacted with four antisera specific for the C-terminal region of gastrin or CCK, but estimates of concentration varied between antisera. Antisera specific for the N-terminus of heptadecapeptide gastrin (G17), intact G17, or the amphibian CCK-like peptide caerulein did not cross react with the crocodile extracts. Gel filtration of the extracts on Sephadex G50 resolved one major peak eluting significantly before G17 or CCK8, suggesting larger molecular size, whereas ion exchange on DE52 cellulose resolved two major immunoreactive peaks, both eluting before G17, indicating that they are less acidic. The more acidic of the two peptides stimulated gastric acid secretion in the rat, but had no CCK-like actions on the rat pancreas. Thus crocodile antrum contains gastrin-like peptides, which are however clearly distinguishable from any of the known mammalian forms of gastrin and CCK.     

Gastrin metabolism in neonatal pigs and grower-pigs.

1. Half-life (1.7 +/- 0.1 min), distribution volume (146 +/- 12 ml/kg) and metabolic clearance rate (28 +/- 1 ml/kg/min) of little gastrin (G17) in neonatal pigs (N = 6; 3-12 days old) were significantly different from those in grower-pigs (N = 4; 161-170 days old) (2.4 +/- 0.1 min; 58 +/- 2 ml/kg; 7.9 +/- 0.3 ml/kg/min, respectively). 2. Half-life (33 +/- 4 min) and distribution volume (265 +/- 33 ml/kg) of big gastrin (G34) in neonatal pigs were greater but not significantly different from those in grower-pigs (24 +/- 2 min; 217 +/- 20 ml/kg, respectively). 3. Half-life of G17 in liver extracts from pigs 2-90 days old (40.4 +/- 4.2 min) was significantly longer than in kidney extracts (22.0 +/- 1.7 min). Half-lives of G34 in liver and kidney extracts from pigs 10-90 days old (78 +/- 6; 74 +/- 4 min, respectively) were significantly shorter than the corresponding values for 2-day-old pigs (134 +/- 3; 149 +/- 9 min, respectively). 4. Since G34 is the major circulating form of gastrin in neonatal pigs the relative longer half-life of G34 to G17 in these animals may contribute to the higher circulating gastrin concentration compared with that in older animals.     

Ontogeny of gastric acidity in the ovine fetus

Hypoacidity and hypergastrinaemia have been reported in the newborn human. However, little is known about in utero gastric acid secretion, and the relationship to fetal plasma gastrin levels. The longitudinal pattern of development of basal and stimulated gastric acid secretion in the non-anaesthetized fetal sheep has been studied during the last 45 days of gestation. Fetuses had cannulae inserted into the jugular vein, carotid artery and stomach. Gastric juice and blood was sampled daily from 101 days gestation until birth (145 days). Intermittent basal acid secretion began between 120 and 133 days of gestation. These fluctuations in gastric juice pH continued until birth. Overall there was a decline in gastric pH from 7.5 +/- 0.2 (SEM), for fetuses 101-105 days to 4.3 +/- 0.5 by 131-135 days. Mean fetal plasma gastrin was higher than maternal levels after 111-115 days but no correlation between fetal plasma gastrin levels and gastric pH could be demonstrated. Pentagastrin and histamine infusion did not stimulate acid secretion in fetuses younger than 115 days. After this age the fetuses became responsive to both pentagastrin and histamine. In contrast, cholinergic stimulation, using bethanechol, did not stimulate acid production until 10 to 15 days later, suggesting a hierarchy in the development of the control of acid secretion in the fetus. The lack of response to endogenous gastrin and the hierarchy in the control of acid secretion suggest either a lack of receptors on the parietal cell or the presence of an inhibitor of acid secretion. These studies are relevant to human physiology since the present findings show that the sheep and human have a similar gastrin/acid profile at birth.     

Implication of gastrin in cyclooxygenase-2 expression in Helicobacter pylori infected gastric ulceration

Gastroduodenal ulcerations have worldwide distribution and the infection with Helicobacter pylori (HP) has been implicated in pathogenesis of this disease. The HP infection is usually accompanied by hypergastrinemia and enhanced generation of prostaglandins (PG), both implicated in the pathogenesis of peptic ulcerations but no study has been undertaken to assess the relationship between the HP infection and coexpression of gastrin and cyclooxygenases (COX), the rate limiting enzymes in the PG production. Since HP infection, usually accompanying peptic ulcerations, results in increased release of gastrin, a potent gastric mitogen that might be capable to induce COX-2 and to generate PG, we decided 1) to compare the seroprevalence of HP and its cytotoxic protein, CagA, in gastric ulcer patients with those in age- and gender-matched controls; 2) to determine the gene expression of gastrin and its receptors (CCK(B)-R) at the margin of gastric ulcer and in the mucosa of antrum and corpus before and after successful eradication of HP, 3) to assess the plasma levels and gastric luminal contents of gastrin before and after HP eradication and 4) to examine the mRNA and enzyme protein expression of COX-1 and COX-2 as well as the PGE2 generation in ulcer margin tissue and gastric antral and fundic mucosa before and after the HP eradication. The trial material included 20 patients with gastric ulcer and 40 age- and gender-matched controls. Anti-HP and anti-CagA IgG seroprevalence was estimated by specific antisera using ELISA tests. Gene expressions of gastrin, CCK(B)-R, COX-1 and COX-2 were examined using RT-PCR with beta-actin as a reference and employing Western blotting for COX-2 expression, while gastrin and PGE2 were measured by RIA. All gastric ulcers were located at smaller curvature within the antral mucosal area. The seroprevalence of HP, especially that expressing CagA, was significantly higher in gastric ulcers (85%) than in controls (62.5%). Both gastrin and CCK(B)-R mRNA were detected by RT-PCR in ulcer margin and gastrin mRNA was overexpressed in remaining antral mucosa, while CCK(B)-R mRNA was overexpressed in fundic mucosa of HP infected patients. Similarly, COX-2 mRNA and protein were found in margin of gastric ulcer and in the HP infected antral and fundic mucosa but not in the mucosa of HP eradicated patients in whom ulcers completely healed and gastrin was expressed only in antrum, CCK(B)-R only in corpus, while COX-1 was detected both in antrum and corpus. HP positive gastric ulcer patients showed about three times higher levels of plasma immunoreactive gastrin and about 50% higher luminal gastrin contents than the HP negative controls and this increased plasma and luminal gastrin was normalized following the HP eradication. A significant fall in gastrin and CCK(B)-R mRNA expression was noticed six weeks after HP eradication in gastric antral and fundic mucosa, while COX-2 mRNA completely disappeared after this treatment. We conclude that 1) HP infected gastric ulcer margin coexpresses gastrin, its receptors (CCK(B)-R), and COX-2; 2) HP infection may be implicated in gastric ulceration via increased release of gastrin that could be responsible for the overexpression of COX-2 that in turn could help ulcer healing through the stimulation of mucosal cell growth, restoration of the glandular structure and angiogenesis in the ulcer area and 3) gastrin produced in HP infected antral mucosa seems to be involved in the induction of COX-2 and PG production by this enzyme and this may contribute to the ulcer healing.     

Function and regulation of gastrin in transgenic mice: a review.

The gastrin gene is expressed in fetal pancreatic islet cells, but in the adult is expressed mainly in the gastric antrum. To study the regulation of the gastrin promoter, we created several transgenes containing the human and rat gastrin 5' flanking regions joined to the coding sequences of the human gastrin gene. The human gastrin transgene contained 1,300 bp of 5' flanking DNA, while the rat gastrin transgene contained 450 bp of 5' flanking DNA. The human gastrin transgene was expressed in fetal islets, but was not expressed in adult gastric antrum. In contrast, the rat gastrin transgene was expressed in adult antral G cells, but no expression was observed in fetal islets. To study the possible role of gastrin as an islet growth factor, a chimeric insulin-gastrin (INS-GAS) transgene was created, in which the expression of the human gastrin gene is driven from the rat insulin I promoter. These INS-GAS mice were mated with mice overexpressing TGF alpha, transcribed from a mouse metallothionein-transforming growth factor alpha (MT-TGF alpha) transgene. While overexpression of gastrin or TGF alpha alone had no effect on islet mass, overexpression of both transgenes resulted in a twofold increase in islet mass. In conclusion, these data indicate that (1) gastrin can interact synergistically with TGF alpha to stimulate islet growth; (2) the human gastrin transgene contains the islet specific enhancer; (3) the rat gastrin transgene contains the antral specific enhancer.     

Progastrin-like immunoreactivity in porcine antrum: identification and characterization with region-specific antisera

In an effort to identify and characterize precursors of gastrin in tissues, we generated region-specific antisera against a synthetic progastrin peptide, Try-Gly-Trp-Met-Asp-Phe-Gly-Arg-Arg (GL9), as deduced from the nucleotide sequence of gastrin mRNA. This antisera did not cross-react with gastrin or progastrin peptides with shorter carboxyl-terminal extensions. Progastrin-like immunoreactivity (PGLI) was measured in porcine antrum at a concentration of 6.8 +/- 1.2 pmol/g wet weight (mean +/- SE, n = 5), or roughly 0.2% of that of gastrin. On Sephadex G50 chromatography, a major peak of PGLI was eluted as a slightly larger molecule than gastrin heptadecapeptide (G17) but possessed the same N-terminal immunoreactivity. These findings suggest that G17 may be formed by processing of a carboxyl-terminally extended precursor as an alternative to cleavage of big gastrin (G34).     

A novel gastrin-processing pathway in mammalian antrum

An antiserum, L221, has been developed that is specific for the C-terminal region of the N-terminal tridecapeptide (i.e., 1-13) fragment of the acid-stimulating hormone, G17. In contrast to N-terminal G17 antisera previously used to estimate 1-13 G17, L221 does not cross-react with other N-terminal gastrin fragments or with C-terminal extensions of G17. Using L221 in conjunction with conventional gastrin antisera, and reversed-phase HPLC, it has been possible to identify in addition to 1-13 G17 a further, formerly unrecognised gastrin fragment, 1-11 G17, in stomach extracts. The production of 1-13 G17, 1-11 G17 and other gastrin forms such as the biologically active hexapeptide G6 which is known to occur naturally cannot be explained by tryptic cleavage of progastrin. Instead, their biosynthesis could be explained by the actions of an enzyme with an endopeptidase 24.11-like specificity. In porcine antrum, unsulphated and sulphated G17 are present in similar amounts, but unsulphated 1-13 G17 was about twice as abundant as sulphate 1-13 G17. This is consistent with previous in vitro findings that endopeptidase 24.11 has a higher affinity for the Ala-11-Tyr-12 and Gly-13-Trp-14 bonds in unsulphated G17, than in sulphated G17. The results suggest a novel albeit minor, processing pathway for gastrin biosynthesis in pig antrum involving an enzyme resembling endopeptidase 24.11.     

Localisation of carcinoembryonic antigen in embryonic and fetal human tissues

Summary Carcinoembryonic antigen (CEA) was localized in various embryonic and fetal human tissues between 8 and 16 weeks of gestation as well as in the colorectal mucosa of older fetuses, newborns and adults. Among the embryonic tissues, CEA was always present in the esophagus, the gastric antrum, the duodenum and the rectum. CEA positive staining of bile cannaliculi of the liver was inconstant. All other embryonic tissues were CEA negative. During early fetal development CEA positive staining of the esophagus, antrum and duodenum was inconstant. However, the whole colon became intensively stained. An inconstant CEA specific staining was found in parts of the midgut and in the bile cannaliculi of the liver. The other organs remained CEA negative. Between the 17th week of gestation and birth, CEA staining pattern of the colorectal mucosa did not change. The staining intensity of late fetal colonic mucosa was similar to that of adult colonic mucosa.Deceased 20th August 1982     

FMRF-amide immunoreactivity in the mammalian gastroenteropancreatic neuroendocrine system

The presence of FMRF-amide, a cardioactive tetrapeptide, was studied by immunocytochemistry in human and rat gastric antrum and pancreas, and in the ovine, bovine, canine and rabbit pancreas. In human and rat gastric antrum, numerous cells contained FMRF-amide immunoreactive material. By staining of serial sections and by double staining, colocalization of immunoreactivity for gastrin and FMRF-amide was observed in part of the gastrin cells. In the pancreas of these and the other species, immunoreactivity for FMRF-amide was located both in acinar and islet endocrine cells. Colocalization of FMRF-amide and pancreatic polypeptide was found in a proportion of pancreatic polypeptide cells in the pancreas. FMRF-amide immunoreactivity never colocalized with the other neurohormonal peptides which occur in the gastric antrum and the pancreas. Our observations show that neuroendocrine cells occur in the gastric antrum and pancreas which are exclusively immunoreactive or gastrin and for pancreatic polypeptide respectively. In addition cells occur which show immunoreactivity for FMRF-amide as well as for gastrin in the gastric antrum and with antiserum to FMRF-amide as well as for pancreatic polypeptide in the pancreas. It is concluded that FMRF-amide antibodies probably recognize a substance in G and PP cells which is not identical but may be structurally related to gastrin and pancreatic polypeptide.     

Conditional deletion of menin results in antral G cell hyperplasia and hypergastrinemia

Antral gastrin is the hormone known to stimulate acid secretion and proliferation of the gastric corpus epithelium. Patients with mutations in the multiple endocrine neoplasia type 1 (MEN1) locus, which encodes the protein menin, develop pituitary hyperplasia, insulinomas, and gastrinomas in the duodenum. We previously hypothesized that loss of menin leads to derepression of the gastrin gene and hypergastrinemia. Indeed, we show that menin represses JunD induction of gastrin in vitro. Therefore, we examined whether conditional deletion of Men1 (Villin-Cre and Lgr5-EGFP-IRES-CreERT2), with subsequent loss of menin from the gastrointestinal epithelium, increases gastrin expression. We found that epithelium-specific deletion of Men1 using Villin-Cre increased plasma gastrin, antral G cell numbers, and gastrin expression in the antrum, but not the duodenum. Moreover, the mice were hypochlorhydric by 12 mo of age, and gastric somatostatin mRNA levels were reduced. However, duodenal mRNA levels of the cyclin-dependent kinase inhibitor p27(Kip1) were decreased, and cell proliferation determined by Ki67 staining was increased. About 11% of the menin-deficient mice developed antral tumors that were negative for gastrin; however, gastrinomas were not observed, even at 12 mo of age. No gastrinomas were observed with conditional deletion of Men1 in the Lgr5 stem cells 5 mo after Cre induction. In summary, epithelium-specific deletion of the Men1 locus resulted in hypergastrinemia due to antral G cell hyperplasia and a hyperproliferative epithelium, but no gastrinomas. This result suggests that additional mutations in gene targets other than the Men1 locus are required to produce gastrin-secreting tumors.     

The ontogeny of regulatory peptide-containing cells in the human fetal stomach: an immunocytochemical study

The antral and fundic regions of the stomachs from 24 human fetuses were examined by immunocytochemistry for the presence of three regulatory peptides (gastrin, somatostatin, and glucagon) and one amine (serotonin (5-HT)) in the epithelial endocrine cells. Gastrin- and somatostatin-containing cells were present at the earliest stage examined (8 weeks). Gastrin cells were restricted to the antrum, while somatostatin cells were found in both the antrum and the fundus. Glucagon-immunoreactive cells were detected from 10 weeks and were confined to the fundus. Serotonin-containing cells were found in both the antrum and the fundus from 11 weeks. Changes in the number of immunoreactive gastrin and somatostatin cells during gestation were quantified. The increase in the number of cells/mm length of vertically sectioned mucosal epithelium best reflects the change in cell population. The peptides and amine studied were found to be contained in separate cell types. Electron microscopic examination of the peptide-containing cells showed that the fetal cells contain granules of similar morphology to their adult counterparts.     

FMRF-amide immunoreactivity in the mammalian gastroenteropancreatic neuroendocrine system

Summary The presence of FMRF-amide, a cardioactiv tetrapeptide, was studied by immunocytochemistry in human and rat gastric antrum and pancreas, and in the ovine, bovine, canine and rabbit pancreas. In human and rat gastric antrum, numerous cells contained FMRF-amide immunoreactive material. By staining of serial sections and by double staining, colocalization of immunoreactivity for gastrin and FMRF-amide was observed in part of the gastrin cells. In the pancreas of these and the other species, immunoreactivity for FMRF-amide was located both in acinar and islet endocrine cells. Colocalization of FMRF-amide and pancreatic polypeptide was found in a proportion of pancreatic polypeptide cells in the pancreas. FMRF-amide immunoreactivity never colocalized with the other neurohormonal peptides which occur in the gastric antrum and the pancreas.Our observations show that neuroendocrine cells occur in the gastric antrum and pancreas which are exclusively immunoreactive or gastrin and for pancreatic polypeptide respectively. In addition cells occur which show immunoreactivity for FMRF-amide as well as for gastrin in the gastric antrum and with antiserum to FMRF-amide as well as for pancreatic polypeptide in the pancreas. It is concluded that FMRF-amide antibodies probably recognize a substance in G and PP cells which is not identical but may be structurally related to gastrin and pancreatic polypeptide.In honour of Prof. P. van Duijn     

Development of gastric proteases in fetal pigs and pigs from birth to thirty six days of age. The effect of adrenocorticotropin (ACTH).

Development of the synthesis and secretion of gastric proteases was studied in 55 Large White x Landrace pigs from 22 days before birth (93 days gestation) to 36 days of age. The pigs came from eight litters and were 0.4 - 13.5 kg body weight. Littermate pairs were treated with either saline or adrenocorticotropin (ACTH) from three days of age. Secretion of protease activity (milk-clotting and general proteolytic activity) was investigated in anaesthetized pigs by a gastric perfusion technique using intravenous infusion of pentagastrin at dose rates of 4 and 8 micrograms/h per kg body weight. In addition, concentrations of protease zymogens (prochymosin, pepsinogen A, progastricsin) were measured in fundic tissue extracts by rocket immunoelectrophoresis. Prochymosin was present in fundic tissue at 22 days before birth, reached peak concentrations at birth and decreased in concentration during the subsequent 36 days. Pepsinogen A and progastricsin were absent or present in trace amounts in the first week after birth, but thereafter concentrations of both zymogens increased rapidly. Development of the pentagastrin-stimulated secretion of protease activity reflected the changes of zymogen concentrations in fundic tissue. Chronic treatment of pigs with ACTH from three days of age significantly increased the concentration of prochymosin in fundic tissue at 9-11 days and the concentrations of pepsinogen A and progastricsin at 34-36 days of age. Hormones such as ACTH and glucocorticoids may therefore play a regulatory role in the ontogeny of porcine gastric proteases.     

Developmental gene expression of gastrin receptor in rat stomach

Gastrin, which is present in fetal plasma, may have important roles in the development of gastric mucosa, since it is not only a potent stimulator of gastric acid secretion but also a growth promoting factor. Gastrin regulates various cellular functions via its receptors on cell membrane. Therefore, in order to elucidate a role for gastrin in the development of gastrointestinal system during gestation, Northern blot analysis was performed. The results of the study suggested that gastrin receptor is mainly present on parietal cells. Furthermore, proton pump and gastrin receptor gene expressions in parietal cells were strongly stimulated by the administration of exogenous gastrin. In conclusion, gastrin may be involved in the developmental change of parietal cells through its receptors.     

Growth pattern of the polypeptide-YY cell population in the upper digestive tract of the rat during the perinatal period and after weaning

Summary The distribution of polypeptide-YY cells within the gastric and duodenal mucosa of the rat and the development of their populations were examined daily from 3 days before birth until day 8 postpartum and after weaning, on day 25 postpartum, using a precise technique of quantification. Polypeptide-YY cells appeared in the stomach around the 19th day of gestation. They were always more numerous in the antral mucosa and particularly in the pyloric sphincter area than in the fundic mucosa. Immunogold staining at the electron-microscopic level revealed that, in the antrum, polypeptide-YY was colocalised with gastrin in endocrine cells mainly of type G and, more rarely, in cells of intestinal type IG. Comparison of the gastrin and polypeptide-YY cell populations in the same rats indicated that, except at day 6 postpartum, there were fewer gastric polypeptide-YY cells than immunoreactive gastrin cells and that polypeptide-YY cells were 8 times less numerous than gastrin cells at day 25 postpartum. Polypeptide-YY cells were clearly present in the duodenum of the 19-day-old embryo. This population increases with age until day 8 postpartum, then significantly decreases (by 87%) between days 8 and 25 postpartum. Because polypeptide-YY may inhibit secretion of gastric acid, it is possible that the presence of significant population of polypeptide-YY cells in the upper digestive tract during the first postnatal week of life may play a role (endocrine or paracrine) in the decreased acid secretion occurring in the newborn rat.     

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.