Histamine containing endocrine cells in the human stomach

Relationships of endocrine cells to each other and to other cell types in the human gastric fundus and corpus

Gastric endocrine cell hormones contribute to the control of the stomach and to signalling to the brain. In other gut regions, enteroendocrine cells (EECs) exhibit extensive patterns of colocalisation of hormones. In the current study, we characterise EECs in the human gastric fundus and corpus. We utilise immunohistochemistry to investigate EECs with antibodies to ghrelin, serotonin (5-HT), somatostatin, peptide YY (PYY), glucagon-like peptide 1, calbindin, gastrin and pancreastatin, the latter as a marker of enterochromaffin-like (ECL) cells. EECs were mainly located in regions of the gastric glands populated by parietal cells. Gastrin cells were absent and PYY cells were very rare. Except for about 25% of 5-HT cells being a subpopulation of ECL cells marked by pancreastatin, colocalisation of hormones in gastric EECs was infrequent. Ghrelin cells were distributed throughout the fundus and corpus; most were basally located in the glands, often very close to parietal cells and were closed cells i.e., not in contact with the lumen. A small proportion had long processes located close to the base of the mucosal epithelium. The 5-HT cells were of at least three types: small, round, closed cells; cells with multiple, often very long, processes; and a subgroup of ECL cells. Processes were in contact with their surrounding cells, including parietal cells. Mast cells had very weak or no 5-HT immunoreactivity. Somatostatin cells were a closed type with long processes. In conclusion, four major chemically defined EEC types occurred in the human oxyntic mucosa. Within each group were cells with distinct morphologies and relationships to other mucosal cells.

Dietary fiber in irritable bowel syndrome (Review)

Irritable bowel syndrome (IBS) is a common chronic gastrointestinal disorder. It is widely believed that IBS is caused by a deficient intake of dietary fiber, and most physicians recommend that patients with IBS increase their intake of dietary fiber in order to relieve their symptoms. However, different types of dietary fiber exhibit marked differences in physical and chemical properties, and the associated health benefits are specific for each fiber type. Short-chain soluble and highly fermentable dietary fiber, such as oligosaccharides results in rapid gas production that can cause abdominal pain/discomfort, abdominal bloating/distension and flatulence in patients with IBS. By contrast, long-chain, intermediate viscous, soluble and moderately fermentable dietary fiber, such as psyllium results in a low gas production and the absence of the symptoms related to excessive gas production. The effects of type of fiber have been documented in the management of IBS, and it is known to improve the overall symptoms in patients with IBS. Dietary fiber acts on the gastrointestinal tract through several mechanisms, including increased fecal mass with mechanical stimulation/irritation of the colonic mucosa with increasing secretion and peristalsis, and the actions of fermentation byproducts, particularly short-chain fatty acids, on the intestinal microbiota, immune system and the neuroendocrine system of the gastrointestinal tract. Fiber supplementation, particularly psyllium, is both safe and effective in improving IBS symptoms globally. Dietary fiber also has other health benefits, such as lowering blood cholesterol levels, improving glycemic control and body weight management.

Recent advances in the diagnosis of irritable bowel syndrome

The symptom-based diagnosis of irritable bowel syndrome (IBS) has not been established in everyday clinical practice, and the diagnosis of this disorder remains one of exclusion. It has been demonstrated that the densities of duodenal chromogranin A, rectal peptide YY and somatostatin cells are good biomarkers for the diagnosis of sporadic IBS, and low-grade mucosal inflammation is a promising biomarker for the diagnosis of postinfectious IBS. Genetic markers are not useful as biomarkers for IBS since the potential risk genes have yet to be validated, and the intestinal microbiota cannot be used because of the lack of an association between a specific bacterial species and IBS. Furthermore, gastrointestinal dysmotility and visceral hypersensitivity tests produce results that are too nonconsistent and noncharacteristic to be used in the diagnosis of IBS. A combination of symptom-based assessment, exclusion of overlapping gastrointestinal diseases and positive biomarkers appears to be the best way to diagnose IBS.

Impairment of gastric secretion modulation in duodenal ulcer and in long-term PPI treatment: quantitative morphologic findings and pathophysiologic implications

Helicobacter pylori affects gastric secretion. This functional effect might have a morphometric counterpart. Therefore, the gastric cell secretory compartment was morphometrically assessed in different pathophysiologic conditions related to Helicobacter pylori infection. Nineteen Helicobacter pylori-positive nonduodenal ulcer subjects, 15 omeprazole chronically treated subjects, and 19 duodenal ulcer patients were studied against 19 controls. Somatostatin, gastrin, enterochromaffin-like, and parietal cell density was assessed in gastric biopsies. No differences in any cell type density were found between Helicobacter pylori-positive nonduodenal ulcer subjects and controls. On the contrary, differences were significant when comparing omeprazole and duodenal ulcer patients to controls (higher density of gastrin, enterochromaffin-like, and parietal cells, lower density of somatostatin cells). In duodenal ulcer a reversion to control values followed Helicobacter pylori eradication and ulcer healing. A direct linear correlation between enterochromaffin-like, gastrin, and parietal cell density was demonstrated. An almost complete map of mucosal cells involved in gastric secretion is provided by this study. The cell density pattern, identical to the omeprazole group, points to an impaired feedback control of secretion in duodenal ulcer. The reversion to control values after Helicobacter pylori eradication and ulcer healing demonstrates the pathogenetic role of Helicobacter pylori-host interaction in these changes.

Histamine immunocytochemistry: a new method for detection of basophils in peripheral blood

We report that basophils in peripheral blood can be stained using histamine immunocytochemistry. The staining is based on the fixation of leucocytes with 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide (CDI) and the subsequent incubation of these cells with antisera raised against histamine conjugated to different carrier proteins using CDI. The staining appears to be specific for basophils and stained cells can be examined using both fluorescence microscopy and flow cytometry. In addition, histamine immunocytochemistry can be combined with conventional immunocytochemistry by incubating leucocytes with antibodies to cell surface antigens prior to or following fixation of the cells with CDI. Thus, histamine immunocytochemistry may be a valuable tool in future studies of human basophils.

Clinical and histopathological tumour progression in ECL cell carcinoids ("ECLomas")

AIMS

The aims of this study were to illustrate the malignant potential of gastric enterochromaffin-like (ECL) cell carcinoids (ECLomas) associated with hypergastrinemia, and the gradual neoplastic progression of such tumours. In addition, we examined whether the tyramide signal amplification (TSA) technique could visualize immunohistochemical (IHC) neuroendocrine (NE) features in the dedifferentiated neoplastic ECL cells which were not detected by conventional methods.

METHODS

Conventional histopathological and IHC methods for visualizing ECL cells and cell proliferation were used in addition to the TSA technique.

OBSERVATIONS

Our patient was followed for 5 years. During that period, her ECLoma displayed all the signs of classical tumour progression, ultimately with the appearance of metastases in the regional lymph nodes, the liver and the skin. The neoplastic ECL cells became progressively dedifferentiated with an increasing number of Ki-67 immunoreactive (IR) cell nuclei. In addition, there was a substantial decrease in argyrophil and IR NE cells that could be visualized by conventional methods. By applying the TSA technique, however, the number of IR tumour cells increased considerably.

CONCLUSIONS

ECLomas secondary to hypergastrinemia should be closely followed for signs of clinical and histopathological tumour progression. Such ECLomas deserve early, active, radical surgical treatment. The TSA technique is a valuable tool for visualizing the characteristic IHC features in dedifferentiated NE cells.

Developmental regulation of gastric somatostatin secretion in the sheep

Gastric somatostatin (SRIF) regulates gastric acidity by inhibiting gastric acid and gastrin secretion. SRIF secretion is increased by gastric acidity and also directly by regulators of gastric acid secretion such as gastrin. This direct effect has not been described in the developing animal, nor have the roles of intermediaries such as histamine and gastric acidity been defined. The present study aimed to establish the regulatory role of gastrin and histamine during development on SRIF secretion and also to determine whether the effects of gastrin and histamine are independent of gastric pH. Pentagastrin and histamine were infused on separate occasions into fetal sheep, newborn lambs, and 28-day-old lambs. To determine the roles of endogenous histamine and gastric pH, ranitidine (a histamine-2 receptor antagonist) and omeprazole (a H+/K+ ATPase inhibitor) were coinfused with the agonists. Plasma SRIF and gastrin concentrations were measured by RIA. Pentagastrin stimulated SRIF secretion in the fetus after 131 days of gestation (term is 147 days), whereas stimulation by histamine was effective only after birth. The SRIF stimulatory effect of pentagastrin in 28-day-old lambs was abolished by ranitidine, which also reduced this effect in the adult sheep. This inhibitory effect of ranitidine was shown to be a result of blockade of stimulatory H2 receptors, because in the adult blockade of acid secretion with omeprazole failed to attenuate the response of histamine. These results indicate that in the fetus, gastrin receptors, but not histamine receptors, are functionally involved in the stimulation of SRIF secretion. After birth, both gastrin and histamine stimulate SRIF, but the effect of gastrin is mediated at least in part by the release of endogenous histamine. These responses occur independently of changes in gastric acidity, supporting the concept of a direct negative feedback between SRIF and gastrin.

Ontogeny of ECL cells in the rat

ECL cells produce histamine and chromogranin A, and are restricted to the oxyntic mucosa of the stomach. ECL cell ontogeny has been studied in some detail in the rat. Using histidine decarboxylase immunostaining, the first ECL cells can be demonstrated at embryonic day 17. Immunoreactive histamine and chromogranin A appear one day later. At embryonic day 20, the vesicular monoamine transporter type 2 is also present in the ECL cells. Neonatally the ECL cell proliferation is slow; however, one to three weeks postnatally there is a rapid growth of ECL cells to populate the basal half of the glands. Gastrin is known to be an important stimulator of ECL cell activity and growth in the adult rat. As revealed in recent mouse gene knock out models gastrin does not seem to play a role in the early ECL cell differentiation and development.

Recognition and the histopathologic classification of ECL cell proliferations

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Carcinoid disease: review of the literature

Carcinoid syndrome is the product of a rare but fascinating malignant neoplasm. Carcinoid syndrome was described more than 100 years ago, and recent advances in diagnostic localization, elucidation of the mechanisms of oncogenesis, treatment options, and, consequently, patient prognosis have been made. Current modalities of treatment, possible therapeutic implications of new avenues of research, and current literature on the chemotherapeutic combinations used are reviewed.

Gastrointestinal endocrine tumours. Pathology

Neuroendocrine tumours can form in any part of the gastrointestinal tract. The most common types are the ECL cell tumours of the oxyntic mucosa of the stomach, G cell tumours of the duodenum, argentaffin, EC cell tumours of the small intestine and L cell tumours of the large bowel. The only well-defined clinical syndromes associated with hormone hypersecretion are ZES, resulting from duodenal gastrinomas, and carcinoid syndrome, caused by malignant argentaffin tumours. Genetic predisposition has been demonstrated for some tumour types, e.g. duodenal gastrinoma in MEN 1 and duodenal somatostatin cell tumours in MEN 2. Other factors predisposing to the genesis of these lesions include circulating hormone levels and the maintenance of chronic inflammatory states. As with most neuroendocrine tumours, malignant potential is difficult to assess on the basis of histology alone and prognostic evaluation depends more on size and evidence of local invasion and/or distant metastases.

Dual inhibitory pathways link antral somatostatin and histamine secretion in human, dog, and rat stomach

BACKGROUND & AIMS

The secretion and function of antral histamine are not known. The aims of this study were to characterize the mechanisms of histamine release from the gastric antrum of humans, dogs, and rats and to determine whether histamine can influence the secretion of somatostatin and gastrin.

METHODS

Somatostatin, gastrin, and histamine secretion from superfused antral segments was measured using radioimmunoassay.

RESULTS

Superfusion with thioperamide (H3 antagonist) increased somatostatin and decreased gastrin and histamine secretion in all three species; superfusion with (r)-alpha-methylhistamine (H3 agonist) had the opposite effect. The pattern implied that endogenous histamine, acting via H3 receptors, exerts an inhibitory paracrine influence on somatostatin secretion, which in turn regulates gastrin secretion. Superfusion with somatostatin antibody increased histamine secretion; the increase was not affected by the gastrin antagonist L-365,260, implying that it was not mediated by the concurrent increase in gastrin but by suppression of an inhibitory pathway linking somatostatin and histamine. Superfusion with methacholine alone and in the presence of either the H3 agonist or antagonist confirmed the existence of reciprocal inhibitory pathways linking somatostatin and histamine.

CONCLUSIONS

Antral histamine in humans, dogs, and rats is linked to antral somatostatin via reciprocal inhibitory paracrine pathways that serve to amplify the regulatory influence of somatostatin.

Gastric mucosal histamine storing cells. Evidence for different roles of mast cells and enterochromaffin-like cells in humans

Gastric mucosal histamine content, enterochromaffin-like cell density, and mast cell density were studied in 13 subjects under omeprazole therapy, 13 partially gastrectomized subjects with a Billroth II reconstruction, 10 partially gastrectomized subjects with a Roux-en-Y reconstruction, and 9 control subjects. Histamine content was significantly greater both in the subjects with higher gastrinemic levels (omeprazole-treated subjects) and those with more abundant enterogastric reflux (Billroth II subjects) than in controls. Enterochromaffin-like cell density was significantly greater in the omeprazole subjects than in each of the other groups. Mast cell density was significantly greater in Billroth II subjects than in controls. Serum gastrin levels, mucosal histamine content, and enterochromaffin-like cell density were positively correlated. Gastrin was not correlated to mast cell density. These results support the existence of different control pathways for enterochromaffin-like and mast cells. Moreover, they suggest that enterochromaffin-like cells and mast cells are involved in the regulation of gastric secretion and in gastric mucosal injury-repair mechanisms, respectively, due to histamine release.

Histamine chloramines have a persistent stimulating effect on histamine H2 receptors and gastric acid secretion

Histamine plays an important role in the control of gastric acid secretion. Recently, chlorinated derivatives of histamine have been identified as having multiple effects on the intestinal tract. The aim of this study was to investigate the role of histamine chloramines on gastric acid secretion. We compared the effects of histamine and histamine chloramines on the histamine H2 receptors in vitro using guinea pigs and on gastric acid secretion in rats. With respect to the effects on histamine H2 receptors, histamine monochloramine showed agonist effects similar to those seen with histamine, but the agonist effects of histamine dichloramine were about half those of histamine. Unlike histamine effects, the histamine H2 receptor agonist effects of histamine monochloramine and histamine dichloramine did not disappear after repeated washout. With respect to the stimulation of gastric acid secretion in vivo, histamine monochloramine was similar to histamine, while the effect of histamine dichloramine was 42.2-52.7% of that of histamine. The recovery time to the basal secretory level after completion of stimulation by histamine chloramines was significantly prolonged compared with histamine. These results suggest that histamine chloramines, which bind strongly with histamine H2 receptors, may delay the termination of gastric acid secretion and increase the burden on the gastric and duodenal mucosa.

Acute responses of rat stomach enterochromaffinlike cells to gastrin: secretory activation and adaptation

BACKGROUND/AIMS

Evidence for gastrin-induced histamine secretion from isolated rat enterochromaffinlike (ECL) cells was presented recently. We have investigated the gastrin-evoked secretory activation and adaptation of ECL cells in intact rats over a time span of a few minutes to several hours.

METHODS

Fasted rats received a maximally effective dose of synthetic human Leu15-gastrin-17 by continuous intravenous infusion. ECL cell ultrastructure and ECL cell-related parameters (e.g., mucosal histamine and pancreastatin concentrations, histidine decarboxylase [HDC] activity, and messenger RNA [mRNA] concentration) were analyzed.

RESULTS

Gastrin reduced the number of cytoplasmic vesicles in ECL cells while reducing the concentrations of histamine and pancreastatin in the oxyntic mucosa. The effects were maximal within a few hours after the start of gastrin infusion. The concentration of pancreastatin in serum was elevated for the duration of the study. The mucosal concentrations of histamine and pancreastatin returned to prestimulation values after 4-6 hours. The HDC activity and mRNA concentration increased progressively until after 6-8 hours of gastrin infusion.

CONCLUSIONS

Gastrin promptly degranulates the ECL cells, releasing histamine and pancreastatin from the vesicles. Synthesis of histamine and pancreastatin is accelerated, a process associated with renewal of vesicles. The increase in HDC activity and mRNA concentration continues for several hours after restoration of the vesicles.

Gut hormones in gastric function

This chapter has focused on many of the gut hormones that regulate gastric function. Gastrin remains the principal, and only, gastric hormone controlling gastric acid secretion during the cephalic, gastric and intestinal phases of secretion. Several other hormones, including cholecystokinin, peptide YY and secretin, released from intestinal endocrine cells in response to food substrates, have significant inhibitory effects on gastric acid secretion. Many of these hormones, including enteroglucagon and glucagon-like peptide, may act through paracrine release of somatostatin, which in turn acts as the final mediator of acid inhibition. In addition, several peptides contained in nerves, including gastrin releasing peptide and vasoactive intestinal peptide, have been shown to regulate gastric acid secretion and motor function. With the creation of specific monoclonal antibodies for use in in vivo immunoneutralization studies, and the development of selective chemical antagonists for use in receptor blockade experiments, the specific contributions of the different gut hormones in the regulation of gastric function, can be assessed.

Cellular and chemical mediators of type 1 hypersensitivity in calves infected with Ostertagia ostertagi: histamine, prostaglandin D2, prostaglandin E2 and leukotriene C4

Plasma histamine, prostaglandin E2 (PG) D2, PGE2, and leukotriene (LT) C4 levels were determined in 26 Holstein steers before and after natural or experimental infection with Ostertagia ostertagi. Post-infection abomasal lymph was also assayed for PGD2, PGE2, and LTC4. Histamine determinations were performed on abomasal tissue from three locations. Results showed that: (1) tissue histamine levels increased in steers with type 2 ostertagiosis, (2) lymphatic PGD2 and PGE2 levels were increased, probably as a result of macrophage activity, (3) lymphatic LTC4 levels increased in steers with type 1 ostertagiosis, and were correlated with tissue eosinophilia, and (4) plasma levels of PGD2, PGE2, LTC4 and histamine were not useful for predicting worm burdens. These findings suggest a functional role for eosinophils and mast cells in the pathophysiology of ostertagiosis, through mediation of a type 1 hypersensitivity reaction.

Reflux-related gastric mucosal injury is associated with increased mucosal histamine content in humans

BACKGROUND

Experimental studies in the dog and the rat have shown histamine involvement in reflux-related gastric mucosal injury. However, no definite demonstrations of a link between reflux-related gastric mucosal injury and mast cell mediators exist in humans.

METHODS

The relationships between reflux, gastric mucosal histamine content, and gastric histology were assessed in partially gastrectomized subjects presumptively with high (11 Billroth II subjects) and low reflux levels (9 total biliary diversion subjects), respectively. Findings were compared with those in a control group consisting of 8 endoscopically and histologically proven normal subjects.

RESULTS

Bile acid quantity and concentration in the gastric aspirates were significantly greater in Billroth II subjects than in total biliary diversion subjects. Significantly higher cumulative scores for foveolar hyperplasia, mucosal edema, capillary dilatation and congestion, and smooth muscle fibers in the lamina propria were found in Billroth II subjects than in total biliary diversion subjects. Mucosal histamine content as well as mast cell density and degranulation differed significantly between Billroth II and the other two groups.

CONCLUSIONS

These results represent the first demonstration in humans of an association between mast cell mediators and chemical gastric mucosal injury.

Neurohormonal regulation of histamine release from isolated rabbit fundic mucosal cells

Histamine-containing cells isolated from rabbit fundic mucosa were found in a small cell elutriation fraction (cells with diameter about 9-12 microns) enriched in mucus and endocrine cells and containing less than 1% mast cells (F1 cells). Gastrin (HG-17), pentagastrin and CCK-8 (C-terminal octapeptide of cholecystokinin) dose-dependently stimulated histamine release (EC50, respectively, 0.126 +/- 0.03, 0.92 +/- 0.15 and 0.211 +/- 0.025 nM) and somatostatin inhibited this release. PGE1, PGE2 and PGD2 alone were unable to enhance histamine release even at high concentrations but, when used in combination with gastrin of CCK-8, the release of histamine caused by these peptides was potentiated (about 1.5- to 2-fold). Carbachol also enhanced the liberation of histamine but with a weaker potency and efficacy than the gastrointestinal peptides (EC50: 1.50 +/- 0.06 microM). The use of specific muscarinic antagonists for M1-, M2- and M3-type receptors led us to conclude that an M1 receptor might be involved in the muscarinic-induced stimulation of histamine release. Activators of protein kinase C, 12-O-tetradecanoylphorbol-13-acetate (TPA) and 1-oleyl-2-acetyl-glycerol (OAG) as well as the calcium ionophore, A23187, induced histamine release, whereas agents which increased intracellular cAMP content were devoid of effect.(ABSTRACT TRUNCATED AT 250 WORDS)

Gastric argyrophil (enterochromaffin-like), gastrin, and somatostatin cells after proximal selective vagotomy in man

The number, size, and volume density of endocrine cells was determined in biopsies obtained endoscopically in patients after proximal selective vagotomy (PSV; N = 31), antrectomy (N = 9), untreated duodenal ulcer (DU) disease (N = 11), and in controls (N = 15). Serum gastrin was significantly elevated after PSV (mean 60 pg/ml) compared to DU patients (29 pg/ml), controls (26 pg/ml), and after antrectomy (11 pg/ml). Volume density of fundic argyrophil (largely enterochromaffin-like) cells after PSV (0.74%) and in DU disease (0.63%) were significantly (P < 0.001) higher when compared with controls (0.37%) but lower after antrectomy (0.24%; P < 0.02). The density of argyrophil cells was not influenced by the interval following PSV or the magnitude of hypergastrinemia. Antral gastrin cells were increased after vagotomy, whereas the antral and fundic somatostatin cell numbers were reduced after PSV. It is concluded that: (1) a major role of the vagal nerve as a trophic factor for enterochromaffin-like cells could not be demonstrated after PSV, and (2) moderate hypergastrinemia after PSV did not induce proliferation of ECL cells.

Enterochromaffin-like cells in the rat stomach: effect of alpha-fluoromethylhistidine-evoked histamine depletion. A chemical, histochemical and electron-microscopic study

In the rat, gastric histamine is stored predominantly in the enterochromaffin-like (ECL) cells, which are located basally in the oxyntic mucosa. The functional significance of histamine in the ECL cells is a matter of speculation. In this study the effect of depletion of histamine on the properties and ultrastructure of the ECL cells was examined. Histamine synthesis was inhibited with alpha-fluoromethylhistidine (3 mg.kg-1.h-1) given via osmotic minipumps over a period of 24 h. The treatment reduced the histidine decarboxylase activity (approximately 20% remaining) and histamine concentration (less than 20% remaining) in the oxyntic mucosa, as well as the intensity of histamine- and chromogranin A-immunostaining in the ECL cells, compared to control rats. The cytoplasmic (secretory) granules/vesicles were greatly reduced in number and size following alpha-fluoromethylhistidine administration. The histamine immunostaining of the mast cells, which occurs at the mucosal surface and in the submucosa, appeared unaffected. We conclude that ECL cell histamine accounts for at least 80% of the total oxyntic mucosal histamine in the rat and that it represents a more mobile pool than mast cell histamine. The reduction in the number and size of the ECL cell granules/vesicles following histamine depletion is in accord with the idea that they represent the storage site for histamine.

Argyrophil cells, mast cells, and histamine in the fundic mucosa of antrectomized patients

Fasting gastrinemia, fundic argyrophil cell density, mast cell number, basal fundic histamine content and histidine decarboxylase activity were determined in 20 antrectomized patients and 20 control subjects. Fasting gastrinemia and fundic argyrophil cell density were significantly lower in antrectomized patients than in controls, whereas fundic mast cell number, basal histamine content, and histidine decarboxylase activity did not differ significantly between the two groups. In antrectomized patients the basal fundic histamine content appears related to the fundic mast cell number, as a consequence of the reduced effect of gastrin on argyrophil cells.

Aspects on diagnosis and treatment of the foregut carcinoid syndrome

Eight patients with the foregut carcinoid syndrome (two gastric and six bronchial primary tumors) are reported. The patients presented with complex clinical symptoms including ectopic production of adrenocorticotrophic hormone and growth hormone-releasing factors. The most alarming symptoms were facial flush and edema, accompanied by severe bronchoconstriction, which easily was misinterpreted as asthmatic attacks. Conventional bronchodilatory drugs may be potentially dangerous in these patients, in whom combined blockade of histamine receptors and treatment with cortisone and octreotide are recommended. Owing to the patients' age and general condition individualized long-term therapy was instituted. Surgical therapy under optimal protection by drugs can be of substantial value also in patients with advanced disease. One patient with life-threatening hormonal symptoms underwent hyperthermic perfusion of the liver with cytotoxic drugs, resulting in good palliation.

Histamine in gastric carcinoid tumors: Immunocytochemical evidence

Gastric carcinoid tumors and nontumorous corpus mucosa from 4 patients suffering from chronic atrophic gastritis associated with pernicious anemia were characterized histochemically, with special reference to the cellular localization of histamine. Tissue sections were also examined for argentaffinity using the Masson technique, for argyrophilia using the Grimelius and Sevier-Munger techniques, and for chromogranin A and serotonin immunoreactivities. The majority of the tumor cells showed the staining characteristics of enterochromaffinlike cells: That is, they exhibited the argyrophil reaction with the Grimelius and Sevier-Munger techniques but lack of argentaffinity, positive histamine and chromogranin A immunostaining, but no serotonin immunoreactivity. Numerous histamine-immunoreactive mast cells were present in the stroma of the tumors and also in the surrounding mucosa. Our findings support the view that gastric carcinoids in patients with hypergastrinemia due to chronic atrophic gastritis are histamine-producing tumors derived from hyperplastic enterochromaffinlike cells.

The biology and pathobiology of the ECL cells

The enterochromaffin-like (ECL) cells represent the predominant endocrine cell population in the acid-producing part of the stomach of both experimental animals and man. These cells actively produce and store histamine in addition to an anticipated but as yet unidentified peptide hormone and are under the control of gastrin. An acute gastrin stimulus causes exocytosis of the cytoplasmic granules/vesicles (and release of histamine and activation of the histamine-forming enzyme, histidine decarboxylase), while a more sustained gastrin stimulus causes first hypertrophy and then hyperplasia of the ECL cells in the rat (at most, a fivefold increase in the cell number). These effects can be demonstrated following infusion of gastrin or following an increase in the concentration of circulating gastrin of endogenous origin. The growth of the ECL cells reflects an accelerated self-replication rate. As studied in the rat, the self-replication rate is accelerated quite soon after induction of hypergastrinemia (blockade of acid secretion), the rate is maximally elevated within two weeks and then declines to control values at ten and 20 weeks despite the sustained hypergastrinemia. Lifelong hypergastrinemia in rats is associated not only with ECL-cell hyperplasia but also with an increased incidence of ECL-cell carcinoids. Recently, we could show that alpha-fluoromethylhistidine, which is a suicide inhibitor of histidine decarboxylase, effectively depletes the ECL cells of histamine and that the histamine-depleted ECL cells respond to gastrin with hyperplasia in a manner identical to normal ECL cells. Other factors beside gastrin seem to participate in the control of ECL-cell function and proliferation. Although exogenous somatostatin is known to suppress the activity of the ECL cells, we have failed to obtain evidence that the somatostatin cells in the oxyntic mucosa play a role in the physiological control of the ECL cells. The vagus, however, is important for the ability of the ECL cells to respond to gastrin. This conclusion is based on the observation that vagal denervation suppresses the hyperplastic response of the ECL cells to gastrin. Porta-cava shunting, on the other hand, greatly enhances the responsiveness of the ECL cells to gastrin. The mechanism behind this effect is unknown.

Studies of isolated parietal and enterochromaffin-like cells from the rat

Rat gastric mucosal cells isolated by enzyme dispersion were separated by elutriation centrifugation. The amount of histamine and the number of enterochromaffin-like (ECL) cells and parietal cells were determined in the crude mucosal cells and the various elutriation fractions. The mucosal cells contained 2.6% ECL and 20% parietal cells. Elutriation centrifugation resulted in good separation of parietal cells and ECL cells. Most of the ECL cells were elutriated in the small cell fractions. Scattered ECL cells were also present in the fraction enriched with parietal cells. Histamine and carbacholine stimulated aminopyrine uptake in a concentration-dependent manner with about the same efficacy, 5.6 times the base-line value. When combined with the phosphodiesterase inhibitor isobutyl methylxanthine, the maximal histamine stimulation was increased to 16.8 times the base-line value, and the sensitivity increased about 10-fold. Gastrin at high and unphysiologic concentrations stimulated only faintly the aminopyrine uptake in parietal cells and the histamine release from ECL cells.

The role of the antrum and the vagus nerve in the metabolism of histamine in the human gastric mucosa

The effects of antrectomy and proximal gastric vagotomy on the metabolism of histamine in the human gastric mucosa were studied in the basal state and during pentagastrin stimulation in patients with duodenal or gastric ulcer disease. Mucosal biopsy specimens were taken from the antral and oxyntic gland areas, whereafter histamine content, histidine decarboxylase activity, and histamine methyltransferase activity were simultaneously assayed. Vagotomy was followed by a decrease in the acid secretory capacity and an increase in basal serum gastrin levels. Histamine content of the oxyntic mucosa increased after vagotomy, but the ability of pentagastrin to form new amounts of the amine was impaired. Antrectomy caused a decrease in acid secretion and a fall in gastrin concentrations. Basal histamine content and rate of amine formation in the remaining oxyntic mucosa were unaffected by antrectomy. Antrectomy impaired the ability of pentagastrin to release histamine. Histamine methyltransferase was not affected by pentagastrin, vagotomy, or antrectomy. In conclusion, both antral gastrin and the vagus nerve seem to exert a regulatory influence on the metabolism of histamine in the human oxyntic mucosa. The withdrawal of these factors either causes impaired ability of pentagastrin to release histamine from its storage site or counteracts the ability of pentagastrin to accelerate histamine synthesis.

"Gastrin" and "CCK" receptors on histamine- and somatostatin-containing cells from rabbit fundic mucosa--I. Characterization by means of agonists

A previous study has suggested the presence of two distinct binding sites for gasrin and cholecystokinin (CCK) in isolated non-parietal cells from rabbit gastric mucosa: a receptor which binds CCK-8 and CCK-39 with a high affinity and a receptor which binds gastrin and CCK-8 with the same high affinity and CCK-39 with a lower affinity. To characterize these receptors, their ability to induce phosphoinositide breakdown was investigated. Gastrin (HG-17), CCK-39 and CCK-8 induced [3H]-inositol phosphate ([3H]InsP) accumulation from [3H]inositol prelabelled cells with a high potency (EC50: 0.3-2.7 nM) but CCK-8 exhibited a higher efficacy than HG-17 or CCK-39. HG-17, CCK-8 and CCK-39 induced a rapid accumulation of [3H]inositol monophosphate ([3H]InsP1), [3H]inositol bisphosphate ([3H]InsP2) and [3H]inositol trisphosphate ([3H]InsP3) but CCK-8 caused a two times higher accumulation than HG-17 or CCK-39. Histamine- and somatostatin-containing cells appeared to be located in this non-parietal cells population. HG-17, CCK-8 and CCK-39 dose-dependently induced histamine release with the following order of potency: HG-17 = CCK-8 (EC50 approximately 0.2 nM) greater than CCK-39 (EC50 approximately 4 nM). In addition, HG-17 exhibited the highest efficacy. HG-17, CCK-8 and CCK-39 enhanced somatostatin-like immunoreactivity (SLI) release with the following order of potency: CCK-8 (EC50 approximately 0.1 nM) = CCK-39 greater than HG-17 (EC50 approximately 10 nM); CCK-8 and CCK-39 exhibited the highest efficacy. These results led us to the following conclusions: (i) existence of a "gastrin-type" and of a "CCK-type" receptor mediating phosphoinositide breakdown in these gastric non-parietal cells. CCK-8 interacts with both receptor-types with the same affinity; (ii) the release of histamine from histamine-containing cells could be induced following "gastrin-type" receptors activation; (iii) somatostatin release from D-cells present in this non-parietal cells population could be induced following "CCK-type" receptors activation.

Ultrastructural demonstration of histamine in human enterochromaffin like cell granules

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Ultrastructural morphometry of gastric endocrine cells before and after omeprazole. A study in the oxyntic mucosa of duodenal ulcer patients

Long-term toxicological experiments with inhibitors of acid secretion were found to induce hyperplasia and eventually carcinoid tumors of the enterochromaffin-like cells of the oxyntic mucosa. To evaluate the effects of 6 months' treatment with omeprazole in humans, the oxyntic endocrine cells were morphometrically investigated at the ultrastructural level in five patients with active duodenal ulcer. No omeprazole-induced changes were found in the volume density of the total endocrine cell population and specific cell types (including the enterochromaffin-like cell) as well as in the other cytological parameters investigated (number of cell profiles per unit area, mean cross-sectional area of cell profiles, nuclear-cytoplasmic ratio, and density of cytoplasmic secretory granules). Both pretreatment and post-treatment values in our patients with duodenal ulcer significantly differed from those of a previous investigation of healthy volunteers with regard to the volume density of enterochromaffin-like cells and non-granulated cells, which increased, and of D cells, which markedly decreased. The latter result may provide a cellular basis for impairment in the paracrine release of fundic somatostatin in peptic ulcer disease. Finally, morphometric data on endocrine cell volume density provided by electron microscopy were found to correlate with those obtained in the same patients using light microscopy techniques (Grimelius silver impregnation and chromogranin A immunostaining). It is concluded that 6 months' treatment with pharmacological doses of omeprazole is devoid of appreciable trophic effect on endocrine cells of human oxyntic mucosa.

The neuroendocrine system of the gut--an update

During the last few years the endocrine stomach has come into focus much due to the side-effects produced by powerful acid blockers. A sustained and marked inhibition of acid secretion in the rat results in hypergastrinemia, with gastrin cell hyperplasia, and a consequent hyperplasia of the ECL cells. This response of the ECL cells was predictable in view of previous observations that sustained hypergastrinemia causes ECL cell hyperplasia. While the gastrin cell hyperplasia levels off at about twice the normal cell density a few weeks after start of treatment, the ECL cells continue to proliferate for months to reach a five-fold higher density than normally. Evidence is accumulating that ECL cells proliferate through self replication. After life-long inhibition of acid production (high doses of ranitidine or omeprazole) or after extirpation of 75% of the acid-producing part of the stomach, ECL cell carcinoids develop. Endocrine cells in the gut often contain more than one putative messenger. Thus, gastrin cells in many species store GABA and peptide YY; in e.g. cat and man they store in addition a xenopsin-like peptide. Neuromedin U and pituitary adenylate cyclase activating peptide (PACAP) have recently been demonstrated in gut nerves. Their role in gut physiology remains to be identified.

Is hypergastrinaemia dangerous to man?

Achlorhydria has been discussed as a possibly dangerous consequence of therapeutic inhibition of gastric acid secretion since the introduction of H2-receptor antagonists. The risk of long-term hypergastrinaemia has only been considered for about 5 years. The reason for this was the demonstration that gastric carcinoids (ECLomas) observed after life-long treatment of rats with the proton pump inhibitor omeprazole could also be produced in rats by other methods leading to long-lasting profound hypergastrinaemia. Such methods were the 80% resection of the oxyntic mucosa or feeding of ranitidine (2000 mg/day) for 2 years. The endocrine tumours corresponded to the gastric carcinoids found in patients with long-lasting hypergastrinaemia due to pernicious anaemia or with a gastrinoma as part of the MEN I syndrome. Neither in animals nor in man could other endocrine tumours or adenocarcinomas of the gastrointestinal tract be related to hypergastrinaemia. Epidemiologic data do not support gastrin dependence of adenocarcinoma of the stomach or the colon. Experimental findings of gastrin effects on tumour growth in vivo and in vitro have been contradictory and may be explained by the presence of gastrin receptors on tumour cells and the role of gastrin as an autocrine growth factor in some of these tumours. Since acid blockade by proton pump inhibitors or H2-receptor blockers dose-dependently increase serum gastrin levels, patients with ranitidine-resistant peptic ulceration receiving long-term treatment with high-dose omeprazole have been followed up with serial gastric biopsy specimens for up to 5 years. Complete healing, moderate hypergastrinaemia, and a slight hyperplasia but no dysplasia of the ECL cells in the oxyntic mucosa have been observed, which seemed to be correlated to chronic gastritis progressing over the years. Despite these negative findings excessive hypergastrinaemia by overdosage of potent drugs for inhibition of gastric secretion should be avoided and monitoring of plasma gastrin levels is recommended in case of long-term treatment.

In vivo catabolism of histamine in the human stomach

The importance of the stomach in the magnitude of excreted amounts of the major histamine metabolite in the urine was studied during total parenteral nutrition in five patients before and after total gastrectomy. In all subjects, a reduction in the 24-h urinary excretion of methylimidazoleacetic acid was observed. No corresponding effect was seen after an operation because of abdominal aortic aneurysm. In patients with duodenal ulcer disease and those submitted to a cholecystectomy because of cholecystolithiasis, we studied the catabolism of histamine in the stomach by injecting 14C-histamine directly into the portal vein and, simultaneously, 3H-histamine intra-arterially to the corpus fundus region of the stomach and subsequently determining the urinary excretion of 14C. 3H-histamine and their basic and acid metabolites, respectively. We found no apparent difference in the pattern of excreted 14C and 3H metabolites between the two patients groups, indicating that the catabolism of histamine in the stomach of patients with duodenal ulcer disease is similar to that in 'healthy' controls.

Proposed mechanism of induction of gastric carcinoids: the gastrin hypothesis

Novel, powerful and long-acting inhibitors of gastric acid secretion include second generation H2-blockers and so-called proton pump inhibitors, such as omeprazole. Gastric carcinoids were found to develop in experimental animals as a consequence of continuous long-term administration of several of these highly effective anti secretory drugs. This unwanted side effect is now thought to reflect the fact (1) that pharmacological blockade of acid secretion results in hypergastrinaemia, and (2) that long-standing hypergastrinaemia gives rise to hyperplasia of certain endocrine cells, the so-called ECL cells, in the gastric mucosa. The carcinoids that develop in the rat stomach after lifelong treatment with antisecretagogues arise from the ECL cells. The proposed sequence of events is acid blockade--hypergastrinaemia--ECL cell hyperplasia--carcinoid. This concept, referred to as the gastrin hypothesis, maintains that the ECL cell hyperplasia (and possibly the carcinoids) is a consequence of long-term continuous hypergastrinaemia.

Histamine metabolism in human gastric mucosa. Effect of pentagastrin stimulation

The metabolism of histamine in the human gastric mucosa was studied in the basal state and during pentagastrin stimulation. Studies were made in healthy volunteers and in patients with peptic ulcer disease. Mucosal biopsies were taken from antral and oxyntic gland areas whereupon histamine content, histidine decarboxylase activity, and histamine methyltransferase activity were simultaneously assayed. Histamine content of the oxyntic gland mucosa was decreased as a consequence of pentagastrin administration in all groups studied, and this decrease was numerically largest in patients with duodenal ulcer disease. Pentagastrin induced a significant increase in histidine decarboxylase activity of the oxyntic gland mucosa with the most profound increase seen in patients with duodenal ulcer. The highest rates of histamine formation were present in the oxyntic mucosa of patients with Zollinger-Ellison syndrome. The activity of histamine methyltransferase was the same in all groups studied and was not changed by pentagastrin. In conclusion, pentagastrin administration in humans is followed by a significant mobilization of histamine only from the oxyntic gland mucosa, an effect that is more pronounced in patients with duodenal ulcer disease.

Gut endocrine and neural peptides

The once exponential growth in the number of new gut endocrine peptides being discovered has become slightly slower in recent years, and expansion of the field of gut hormones has involved mainly the application of new investigative methods. Some new peptides have been described and major inroads have been made into establishing the ontogeny of gut endocrine cells, the origins and pathways of the enteric innervation, and the involvement of the diffuse neuroendocrine system as a whole in disease states. Further insight is being gained into the functional activity of the peptide cell system by studying the control, sites and rates of peptide gene expression, and the localization and characterization of peptide binding sites on target cells.