Immunoreactive Gastrin Research Articles

Co-localization of xenopsin and gastrin immunoreactivity in gastric antral G-cells

Co-localization of xenopsin and gastrin immunoreactivity in gastric antral G-cells

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.

Intestinal metaplasia of the gallbladder: A morphologic and immunocytochemical study

The morphologic spectrum of intestinal metaplasia was studied in 49 gallbladders that had been excised because of cholelithiasis. Based on the absence or presence of endocrine cells, the cases of intestinal metaplasia were arbitrarily divided into two groups. The gallbladders from the first group (26 cases) contained isolated or small clusters of mature goblet cells, while those from the second group (23 cases), in addition to the goblet cells, contained argyrophil and argentaffin cells and, less frequently, Paneth cells and gland-like structures similar to colonic crypts. Pseudopyloric glands and superficial gastric-type epithelium were present in both groups. Argyrophil cells outnumbered argentaffin cells by a ratio of 4 to 1. By immunocytochemical methods serotonin-containing cells were found to be the most common endocrine cells. Other endocrine cells showed immunoreactivity for somatostatin, cholecystokinin, gastrin, and pancreatic polypeptide. The presence of gut endocrine cells and Paneth cells in the pseudopyloric glands suggests that these glands are also an integral component of intestinal metaplasia of the gallbladder. The findings support the hypothesis that cholelithiasis induces the appearance of a stem endodermal cell that, in turn, may differentiate into cells with mature intestinal or gastric phenotypes.

Concomitant Neuropeptide-Producing Endometrial Carcinoma and Ileal Carcinoid Tumors

The concomitant occurrence of neuropeptide-reactive endometrial carcinoma and ileal carcinoid tumor represents an observation that has been unreported until now. We have seen two patients with this rare combination of tumors. The endometrial carcinomas in these cases manifested focal immunoreactivity for neuron-specific enolase; in addition, one contained rare cells showing positive staining for gastrin, and the other displayed focal content of substance P. The carcinoid tumors seen in each case demonstrated immunocytochemical positivity for neuron-specific enolase and vasoactive intestinal polypeptide, and one also exhibited immunoreactivity for gastrin. Whether this association of neoplasms represents a syndromic complex or a coincidence is a matter of speculation at present.

Co-localization of xenopsin and gastrin immunoreactivity in gastric antral G-cells.

Studies indicating evidence for the presence of the amphibian octapeptide xenopsin in gastric mucosa of mammals prompted us to investigate the cellular localization of this peptide. Using the peroxidase-antiperoxidase method and a specific antiserum to xenopsin (Xen-7) on paraffin and adjacent semithin sections of gastric antral mucosa from man, dog, and Tupaia belangeri, we found numerous epithelial cells showing a specific positive immunoreaction. These cells were of typical pyramidal shape and could be classified as of the "open" type. Cell quantification in serial sections processed for xenopsin and gastrin immunoreactivity, respectively, revealed an identical number of cells per section and an identical distribution of these cells in the middle zone of the antral mucosa. Furthermore, adjacent semithin sections demonstrated the colocalization of xenopsin and gastrin immunoreactivity within the same G-cell. The xenopsin antiserum could be completely absorbed with synthetic xenopsin but not with gastrin. Preabsorption tests with neurotensin, a xenopsin related peptide, or with somatostatin, glucagon, and enkephalins gave no evidence for crossreactivity of the xenopsin antiserum with these peptides. It is concluded that gastric antral G-cells in addition to gastrin also contain the amphibian peptide xenopsin.

Merkel cell tumor of the skin: An immunohistochemical study

Skin biopsy specimens from 12 elderly patients with Merkel cell tumors were investigated. Conventional light microscopy and immunohistochemical techniques were used. All of the tumors had similar morphologic features. Immunoreactivity for neuronspecific enolase, gastrin, calcitonin, and epithelial membrane-like antigen was demonstrated, and both neurofilaments and keratin filaments were observed. The immunohistochemical findings supported a Merkel cell origin for these Merkel cell tumors. The co-expression of neuroendocrine and epithelial markers in Merkel cell carcinomas is suggestive of neuroendocrine differentiation in a neoplasm of epithelial origin. Merkel cell carcinomas share many characteristics with neuroendocrine tumors of the bronchopulmonary and gastrointestinal tracts. All of these neoplasms may originate from cells of similar types that are present in several organs.

Partial purification of a novel stimulant of gastric acid secretion from canine non-antral mucosa

A novel stimulant of gastric acid secretion was extracted and purified from the non-antral gastric mucosa of the canine stomach and some of its biological properties were examined. Tissue was boiled in water and extracted in 2% trifluoroacetic acid. The stimulatory activity was purified by a combination of reverse-phase high pressure liquid chromatography (HPLC) and gel filtration. Fractions were assayed for a stimulation of basal, pentagastrin-and histamine-stimulated gastric acid secretion in the anaesthetized rat. Stimulatory activity was eluted from reversephase HPLC columns with acetonitrile and its elution from Sephadex G-10 and G-50 columns suggested a molecular weight of 1,000 to 3,000. The highly purified extracts enhanced basal, pentagastrin-and histamine-stimulated acid secretion in the rat. A stimulatory fraction was purified which was devoid of immunoreactive gastrin and gastrin-releasing peptide and contained only small amounts of histamine. Its chromatographic properties differed from those of histamine and acetycholine. On two occasions the stimulant was purified to homogeneity and found to contain amino acids. Insufficient pure material was obtained for full characterization. The stimulant has been tentatively called oxyntin.

Plasma gastrin levels in cows at various growing stages.

Plasma gastrin levels before and after feeding were determined by radioimmunoassay in cows at various ages. Pre-feeding levels of immunoreactive gastrin (IRG) increased with age to the maximum value (190.8±27.0pg/ml) in 4-month-old calves weaned immediately before and thereafter decreased gradually to adult low levels (69.1±17.6pg/ml). Suckling calves were fed colostrum and then whole milk at 12-hour intervals. Plasma IRG levels increased rapidly after the 1st suckling and remained high (700-1, 300pg/ml) until 42-54 hours after birth. This hypergastrinemia disappeared suddenly at 60 hours after birth and gastrin levels returned to the pre-suckling levels. In 1-month-old calves, plasma IRG levels attained at a peak value of 100-160pg/ml 2-4 hours after suckling, and decreased gradually to 51.0±6.7pg/ml by the next suckling. Elevations of the IRG level after suckling were variable between 2- to 3-month-old. Weanlings were fed 3 times daily hay, haylage, and concentrated ration. In 4- to 13-month-old calves, large fluctuations occurred irrelatively to feeding. In 14- to 16-month-old calves and adult cows, IRG levels were remained constant without specific post-prandial responses.

Primary Neuroendocrine Carcinoma of the Liver

A case of primary neuroendocrine carcinoma in an unusual location, the liver, is reported. The neoplasm was composed of small, uniform cells that had distinct borders and grew in strands, ribbons and nests; its appearance resembled that of a carcinoid. Electron microscopy and special staining of the neoplastic cells confirmed the neuroendocrine nature of the tumor, and the cells showed immunoreactivity for gastrin and pancreatic polypeptide by the PAP. The recent literature is reviewed, and the possible histogenesis of hepatic neuroendocrine carcinoma is discussed.

Studies on peptides. CXLV. Synthesis of a 27-residue peptide amide corresponding to the entire amino acid sequence of canine gastrin-releasing polypeptide (cGRP).

Canine gastrin-releasing polypeptide (cGRP, characterized as a bombesin-like 27-residue peptide) was synthesized by successive azide condensations of 7 peptide fragments of established purity, followed by deprotection with trifluoromethanesulfonic acid in trifluoroacetic acid. Prior to deprotection, the Met(O) residue in the protected cGRP was reduced by brief treatment with phenylthiotrimethylsilane in the presence of a catalytic amount of trimethylsilyl trifluoromethanesulfonate. The homogeneous HPLC-purified product induced a significant increase of immunoreactive gastrin level in rat plasma, like synthetic human GRP.

Studies on peptides. CXL. Synthesis of human gastrin-releasing polypeptide (hGRP).

Human gastrin-releasing polypeptide (hGRP), which consists of 27 amino acid residues with a C-terminal amide, was synthesized by a conventional solution method, by assembling six peptide fragments followed by deprotection with 1M trifluoromethanesulfonic acid-thioanisole in trifluoroacetic acid. Met(O) employed was reduced by treatment with phenylthiotrimethylsilane in the presence of trimethylsilyl trifluoromethanesulfonate before deprotection. The synthetic peptide was as active as synthetic porcine GRP, in terms of immunoreactive gastrin release in rats.

Radioimmunoassay of gastrin in human saliva.

We have developed a personal procedure for the radioimmunoassay of gastrin (lower detection limit 3 pg/ml). Using 5-fold concentrated lyophilized salivary samples, we are able to detect the basal content of gastrin immunoreactivity in saliva of normal fasting people (mean +/- SD: 1.38 +/- 0.61 pg/ml) compared to plasma gastrin (mean +/- SD: 28.88 +/- 11.00 pg/ml). We found that after meal stimulus, the value of salivary as well as plasma gastrin concentration increased (the correlation coefficient r among salivary and plasma gastrin being 0.899; p less than 0.001). We believe that gastrin appears in a very low concentration in saliva and that it is not produced by the gland, but derives probably from the serum clearance.

Heterotopic Gastric Mucosa in a Perforated Appendix

A fifty-five year old male with an appendicular abscess had 100 ml of pus drained from the right lower quadrant. Two months later, an interval appendectomy was performed. The macroscopically normal appendix had a portion of fibroadipose mesoappendix attached. Microscopic evaluation using routine stains showed redundance and diverticular extrusion as well as foci of ectopic gastric glands. Immunohistological studies for detection of gastrin immunoreactivity revealed gastrin containing cells in foci of ectopicgastric glands. This represents the first report in which gastrin was demonstrated in an appendix, confirming the presence of heterotopic gastric mucosa.

Canine bombesin-like gastrin releasing peptides stimulate gastrin release and acid secretion in the dog.

The synthetic mammalian bombesin-like peptides, canine gastrin releasing peptide 27, 23 and 10, and porcine gastrin releasing peptide 27 were compared with amphibian bombesin 14 and 10 during intravenous infusions into six conscious dogs with chronic gastric cannulae. Gastrin and gastrin releasing peptide were measured in peripherally sampled venous blood by radioimmunoassay and gastric acid secretions were collected. All forms of gastrin releasing peptide stimulated gastrin release and gastric acid secretion in a dose-dependent manner. The larger canine and porcine peptides were more potent than the decapeptide. Bombesin 14 was more potent than bombesin 10. A rise in the venous concentration of immunoreactive gastrin releasing peptide of only 20 fmol ml-1 stimulated gastrin release to about 50% of maximal. Gastrin releasing peptide 10 was cleared from the circulation three times faster than the larger forms and this may account for the apparent differences in potency.

Identification by specific radioimmunoassay of two novel peptides derived from the C-terminus of porcine preprogastrin

A radioimmunoassay has been developed using antibodies to a synthetic analogue of the C-terminal hexapeptide sequence of the porcine gastrin precursor. Boiling water extracts of porcine antral mucosa contained immunoreactive material that diluted in parallel with standard peptide. Concentrations of immunoreactivity were 5.5 ± 0.8 nmol · g −1 (mean ± S.E.M.) in antral mucosa and were closely similar to those of C-terminal heptadecapeptide gastrin immunoreactivity (5.0 ± 0.6 nmol · g −1). Approximately 30-fold lower concentrations were found in porcine duodenum. A similar distribution was found in ferret, but human, rat and chicken antrum did not contain significant quantities of immunoreactivity. Gel filtration of porcine antral extracts on Sephadex G-50 revealed a single peak of immunoreactivity eluting in a similar position to G17, but on anion-exchange chromatography two peaks of immunoreactive material were separated. These also differed in their retention time on reverse phase HPLC. Both peptides are probably derived by tryptic cleavage at the C-terminus of porcine preprogastrin. No evidence was found to suggest that there are significant quantities of unprocessed preprogastrin in hog antral mucosa. The precise chemical difference between the two immunoreactive peptides identified here remains to be established; together, however, they provide specific markers for progastrin synthesis.

Vagal regulation of GRP, gastric somatostatin, and gastrin secretion in vitro.

The effect of electrical stimulation of the vagus nerves on the release of immunoreactive gastrin-releasing peptide (GRP), gastrin, and somatostatin was investigated using the isolated perfused rat stomach. Electrical stimulation (10 Hz, 1 ms duration, 10 V) of the peripheral end of the subdiaphragmatic vagal trunks produced a significant increase in both GRP and gastrin but a decrease in somatostatin. The infusion of atropine sulfate at a concentration of 10(-5) M augmented GRP release and reversed the decrease in somatostatin release in response to vagal stimulation to an increase above basal levels. However, the gastrin response to vagal stimulation was not affected by atropine. The infusion of hexamethonium bromide at a concentration of 10(-4) M significantly suppressed GRP release but did not affect gastrin secretion in response to vagal stimulation. On the other hand, the somatostatin response to vagal stimulation was completely abolished by hexamethonium. These findings lead us to conclude that the intramural GRP neurons might play an important role in the regulation of gastrin as well as somatostatin secretion and that somatostatin secretion may be controlled not only by a cholinergic inhibitory neuron but also by a noncholinergic, e.g., peptidergic stimulatory neuron, both of which may be regulated through preganglionic vagal fibers via nicotinic receptors. In addition, because the infusion of 10(-7) M GRP suppressed the somatostatin secretion, we suggest that either GRP should be excluded from the list of candidates for the noncholinergic stimulatory neurotransmitter for somatostatin secretion or that there are different mechanisms of action for endogenous and exogenous GRP.

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.

Effect of chronic ethanol consumption on the pancreas of the hamster.

The purpose of this study was to determine the effect of chronic ethanol consumption on pancreatic morphology and biochemistry in the hamster, with special attention to lipid changes. A control group of Syrian golden hamsters fed a synthetic liquid diet was compared to an ethanol group pair-fed the same diet with ethanol substituted for 35% of the carbohydrate calories. The animals were sacrificed at 7 weeks and 3, 6, 9, and 12 months. After 12 months of ethanol consumption, a significant decrease in pancreatic triglycerides and a significant increase in pancreatic RNA was seen. These changes were associated with a rise in pancreatic weight and protein content in the ethanol group, reversing a six-month decline in these values. This rise in RNA and protein in the ethanol-treated group corresponded with the appearance of large abnormal zymogen granules. Other ultrastructural features such as lipid droplets, mitochondria, and endoplasmic reticulum were not altered by ethanol. Ethanol did increase the water content of the pancreas. Although ethanol had no effect on the fasting levels of insulin or pancreatic polypeptide, the fasting serum gastrin immunoreactivity was significantly lower in the ethanol animals. This study shows that chronic ethanol consumption produces a metabolic change in the hamster by 12 months which is suggestive of increased protein synthesis with a decrease in pancreatic triglycerides and no lipid droplet formation.

Hypergastrinemia and achlorhydria in chronic renal failure.

In 68 patients with chronic renal failure (CRF), 15 patients with duodenal ulcer and 15 normal subjects, basal plasma gastrin levels and basal and stimulated gastric acid secretion were measured. Two antisera were used: antiserum R2702 with specificity for human G34 and its N-terminal fragments [G34] and antiserum 2604 with specificity for the four main components of gastrin (total gastrin). Basal gastrin concentrations of both total gastrin and G34-like immunoreactivity (G34LI) were significantly higher in the CRF patients than in the other two groups, irrespective of dialysis. Total gastrin levels were not correlated with serum creatinine levels. Total gastrin levels were significantly decreased during hemodialysis, but G34LI levels showed no significant change. A small amount of total gastrin was detected in the dialysate by antiserum 2604. As to the postprandial gastrin release, in the first 30 min, the pattern of response in the patients with CRF was similar to that of the normal subjects, but the peak value was attained later, and the response was more rather prolonged. Gastric analysis showed a low basal acid out put and impaired acid secretion in response to secretagogue. It is concluded that (1) one of the predominant circulating forms of gastrin in CRF is G34LI, and (2) the hypergastrinemia in the CRF patients is probably due to reduced removal of gastrin by kidneys, increased gastrin production by impairment of the negative acid feedback mechanism induced by parietal cell dysfunction or reduced parietal cell sensitivity to gastrin by atrophic gastritis.

Vincristine-induced abnormalities of gastrointestinal regulatory peptide cells of the rat

The microtubule-disrupting drug vincristine is a common component of anti-cancer chemotherapeutic regimes, which produces acute constipation as a side effect. Although generally attributed to damage to the myenteric plexus, the precise mechanism of this disturbance is unknown. In addition, vincristine causes marked aberrations in the secretory response of pancreatic endocrine tissue in both man and rats. No information is available on its possible effect on regulatory peptides of the gastrointestinal tract. In this study we have produced vincristine-induced constipation in rats at a dosage comparable with that employed in the treatment of human subjects. Immunocytochemistry revealed concomitant disturbances in cells exhibiting immunoreactivity for gastrin in the antrum, for gastric inhibitory polypeptide and 5-hydroxytryptamine in the duodenum, for enteroglucagon in the colon, and for somatostatin in all three sites. These widespread effects are transient in nature with normal cell numbers and morphology being reestablished within 6 days. It is suggested that the observed effects are a direct result of microtubule disruption and that gastrointestinal regulatory peptide and amine immunoreactive cells have a rapid regeneration potential.