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Background & Aims: Apart from its importance as an acid secretogogue, the role of histamine as a downstream target of gastrin has not been fully explored. Previous studies have shown that the combination of hypergastrinemia and Helicobacter infection resulted in accelerated gastric cancer in mice. We used this model to examine the role of cholecystokinin 2 (CCK2)/gastrin receptor and histamine H2-receptor signaling in the development of gastric atrophy and cancer. Methods: Male hypergastrinemic mice (INS-GAS mice) were infected with Helicobacter felis and given the CCK2/gastrin receptor antagonist YF476 and/or the histamine H2-receptor antagonist loxtidine for 3 or 6 months. In addition, mice were treated with omeprazole alone or in combination with either YF476 or loxtidine for 3 months. Results: Mice treated with YF476 or loxtidine alone showed partial suppression of both gastric acid secretion and progression to neoplasia. The combination of YF476 plus loxtidine treatment resulted in nearly complete inhibition of both parameters. YF476 and/or loxtidine treatment did not alter the overall level of H felis colonization but did result in significant down-regulation of the growth factors regenerating gene I and amphiregulin. Loxtidine treatment, with or without YF476, induced a mild shift in T-helper cell polarization. In contrast, omeprazole treatment resulted in mild progression of gastric hyperplasia/dysplasia, which was ameliorated by the addition of YF476 or loxtidine. Conclusions: The combination of CCK2/gastrin- and histamine H2-receptor antagonists has synergistic inhibitory effects on development of gastric atrophy and cancer in H felis/INS-GAS mice, while the proton pump inhibitor showed no such effects. These results support an important role for the gastrin-histamine axis in Helicobacter-induced gastric carcinogenesis.

BACKGROUND & AIMS: GATA transcription factors may regulate gene expression in developing tissues, including gut epithelium. In the stomach, their expression has been linked to regulation of proton pump genes. However, GATA consensus sequences also occur in the promoter of the histidine decarboxylase gene, located in enterochrommafin-like cells. The aim of this study was to determine if GATA factors are located in gastric endocrine cells and to examine their expression during development and in response to changes in the gastric luminal environment. METHODS: Polymerase chain reaction cloning, Northern blot, and gel shift assays were used to examine GATA expression in gastric endocrine cells; changes in GATA messenger RNA during development and in response to fasting, feeding, and gastric achlorhydria were determined by Northern blot. RESULTS: GATA-6 was expressed strongly in rodent gastric endocrine cell fractions, in a human ECL cell tumor, and in an endocrine cell line (STC-1) derived from gut epithelium; proteins from STC-1 cells bound specifically to GATA consensus sequences in the human histidine decarboxylase promoter. GATA messenger RNA abundance was up-regulated during terminal differentiation of the rat stomach and on feeding after a fast. CONCLUSIONS: The GATA-6 transcription factor is expressed in gastric endocrine cells and is a potential regulator of gastric differentiation and of genes involved in the response to feeding. (Gastroenterology 1997 May;112(5):1559-67)

BACKGROUND & AIMS: Histamine-producing enterochromaffin-like (ECL) cells play an integrative role in the regulation of acid secretion. Decreased mucosal histamine concentrations and increased levels of interleukin (IL) 1 beta, IL-6, and IL-8 have been detected in the gastric mucosa inflamed with Helicobacter pylori. The aim of this study was to investigate the response of isolated ECL cells to these cytokines. METHODS: Enriched rat gastric ECL cells (85%-95%) were cultured for 2-4 days. RESULTS: Polymerase chain reaction showed IL-1 and IL-6, but not IL-8 receptors, in ECL cell complementary DNA. Positive receptor staining with biotinylated IL-1 beta corresponded to ECL cell enrichment (92%). IL-6 and IL-8 had no effect on histamine secretion. IL-1 beta (2 U/mL) stimulated basal histamine secretion and nitric oxide production within 60 minutes and cyclic guanosine monophosphate production within 20 minutes. Pretreatment for 20 minutes with IL-1 beta (2 U/mL) attenuated gastrin-stimulated histamine secretion by 40%-50%, reversed by the IL-1 receptor antagonist (10 U/ mL). Pretreatment for 20 minutes with IL-1 beta (2 U/mL) completely inhibited gastrin-stimulated (1 nmol/L) histidine decarboxylase activity. IL-1 beta (2 U/mL, 60 minutes) increased lactate dehydrogenase release to 25% of cell content. Cells pretreated with IL- 1 beta did not respond to gastrin after a further 48-hour culture and showed decreased histamine content. CONCLUSIONS: ECL cells appear to express IL-1 receptors. IL-1 beta causes sustained functional impairment of ECL cells in vitro. (Gastroenterology 1997 Feb;112(2):364-75)

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 Leu 15 -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.

Background: In vivo studies have suggested an important role for gastric enterochromaffinlike (ECL) cells in mediating acid secretion. Direct evidence for this function is lacking and requires a preparation of highly purified ECL cells. This work investigates the possible role and mechanism of histamine release from the ECL cell in the peripheral regulation of acid secretion, using purified ECL cells from rat fundic mucosa. Methods: A combination of elutriation and density-gradient centrifugation was used to purify rat fundic ECL cells. Enrichment was determined by the presence of acidic vacuoles containing a V type adenosine triphosphatase, electron microscopy, immunostaining, and histamine content and release. Results: ECL cells were enriched at least 65-fold with respect to the fundic epithelium. Gastrin (EC 50 0.2 nmol/L) and cholecystokinin octapeptide (nonsulfated, EC 50 0.04 nmol/L) stimulated histamine release in a time- and dose-dependent manner, suggesting a CCK-B receptor subtype, confirmed by the inhibition of gastrin/CCK stimulation with the CCK-B antagonist L365,260. Somatostatin also inhibited gastrin-mediated histamine release. Single cell imaging showed that gastrin elevated intracellular cytosolic calcium concentration biphasically. Carbachol and the C kinase activator 120-tetradecanoylphorbol-13-acetate also stimulated histamine release. Epinephrine (blocked by propranolol), forskolin, and dibutyryl-5′-cyclic adenosine monophosphate were also effective, implicating a β-adrenergic pathway. The H 3 agonist R-α-methyl-histamine inhibited, whereas the H 3 -antagonist thioperamide potentiated gastrin/CCK stimulated histamine release. Conclusions: These in vitro results support a central role for the ECL cell in the peripheral regulation of gastric acid secretion.

In the rat, gastric histamine is stored mainly in the enterochromaffinlike cells. Gastrin releases histamine from these cells, and long-term hypergastrinemia results in hyperplasia. The effect of sustained hypergastrinemia on histamine-depleted enterochromaffinlike cells was studied by measuring histidine decarboxylase activity and histamine concentrations and by using quantitative histology. Hypergastrinemia maintained for 6 weeks was induced by inhibition of gastric acid secretion with omeprazole (400 mumol.kg-1.day-1) given orally, and histamine synthesis was inhibited for the same length of time with alpha-fluoromethylhistidine (3 mg.kg-1.h-1) given via osmotic minipumps. In rats given omeprazole alone, the effects of the resulting hypergastrinemia on the enterochromaffinlike cells was reflected in increased histidine decarboxylase activity, increased histamine concentration, and increased number of enterochromaffinlike cells. The general trophic effects on the stomach were seen as increased stomach and oxyntic mucosal weight and increased mucosal thickness. Treatment with alpha-fluoromethylhistidine plus omeprazole markedly reduced the histidine decarboxylase activity and histamine concentration, but the weight of the stomach and oxyntic mucosa, the enterochromaffinlike cell density, and intensity of histidine decarboxylase immunostaining were increased to at least the same extent as after omeprazole alone. These observations indicate that enterochromaffinlike cell histamine is not important for a full expression of gastrin-evoked trophic effects in the stomach.

The enterochromaffinlike cells in the rat stomach are rich in histamine and are thought to be under the influence of gastrin. The effect of sustained endogenous and exogenous hypergastrinemia on the activity and proliferation rate of the enterochromaffinlike cells was studied by determining the histidine decarboxylase activity and histamine concentration and by combining histamine immunocytochemistry and autoradiography after in vivo labeling with [ 3 H]thymidine. The proliferation rate of the stem cells in the oxyntic mucosal progenitor zone was also studied. Exogenous hypergastrinemia was induced by infusion of rat gastrin-17 (60 nmol · kg −1 · day −1 ). Endogenous hypergastrinemia was induced by inhibition of gastric acid secretion with omeprazole (80 μmol · kg −1 · day −1 ) or ranitidine (1200 μmol · kg −1 · day −1 ). The effect of omeprazole was also studied in antrectomized rats. In intact rats, all treatments resulted in elevated plasma gastrin levels and were accompanied by an increase in the histidine decarboxylase activity and the histamine content of the oxyntic mucosa. This resulted in an increase in the enterochromaffinlike cell proliferation rate, leading to enterochromaffinlike cell hyperplasia. The number of labeled stem cells was increased, but this effect was not as pronounced as in the enterochromaffinlike cells. In antrectomized rats, the inhibition of acid secretion by omeprazole did not result in elevated plasma gastrin or in an increase in the activity or number of enterochromaffinlike cells, indicating that omeprazole per se had no effect on these cells. These data support the view that gastrin stimulates the proliferation rate of both enterochromaffin-like cells and stem cells. Gastrin also stimulates the activity of the enterochromaffinlike cells.

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.

Background & Aims: Inducible histamine and histamine H2-receptors have been suggested to be involved in innate immune response. Methods: We examined a functional role of inducible histamine in the protection against hepatic injury and lethality in Propionibacterium acnes-primed and lipopolysaccharide-induced hepatitis, using histidine decarboxylase knockout and H2-receptor knockout mice. Results: Lipopolysaccharide challenge after Propionibacterium acnes priming increased histidine decarboxylase activity in the liver of wild-type mice, associated with a marked elevation of histamine turnover. Histidine decarboxylase-like immunoreactivity was observed in CD68-positive Kupffer cells/macrophages. Treatment of wild-type mice with famotidine or ranitidine but not d-chlorpheniramine augmented hepatic injury and inhibited the survival rate significantly. The same dose of Propionibacterium acnes and lipopolysaccharide induced severe hepatitis and high lethality in histidine decarboxylase knockout and H2-receptor knockout mice; the former were rescued by the subcutaneous injection of histamine. Immunohistochemical study supported the protective role of histamine against the apoptosis of hepatocytes. Histamine suppressed the expression of IL-18 and tumor necrosis factor α in the liver, leading to the reduced plasma levels of cytokines including IL-18, TNF-α, IL-12, IFN-γ, and IL-6. Conclusions: These findings as a whole indicated that endogenously produced histamine in Kupffer cells/macrophages plays a very important role in preventing excessive innate immune response in endotoxin-induced fulminant hepatitis through the stimulation of H2-receptors.

Background & Aims: Histamine, gastrin, and acetylcholine are known to be the primary secretagogues of gastric acid secretion, but how the roles are shared among these secretagogues remains to be fully clarified. To evaluate the cooperation between histamine and the other secretagogues, acid secretion responses induced by each secretagogue were measured in L-histidine decarboxylase (HDC)–deficient mice. Methods: Acid secretion was measured by the titration of acid under anesthesia. The expression of selected genes involved in acid secretion was determined by Northern blot and/or immunoblot analysis. Histamine-2 (H 2 ) receptor binding in the gastric mucosa was investigated using [ 3 H]tiotidine. Results: HDC-deficient mice showed low basal and high exogenous histamine-stimulated acid secretion. The mutant mice showed hypergastrinemia and did not undergo acid secretion upon treatment with exogenous gastrin. However, carbachol stimulated weak and transient acid secretion in the mutants. The Bmax values for H 2 and the expression of Gsα in gastric mucosal membranes were higher in the mutants than in the wild-type mice. Conclusions: This study confirms the concept that histamine production is essential for gastric acid secretion induced by gastrin, but not for that induced by carbachol. HDC-deficient mice should be a suitable model for further functional analyses of the correlation between histamine and the other acid secretagogues. GASTROENTEROLOGY 2002;122:145-155

Background & Aims: Enterochromaffin-like (ECL) cells are histamine-containing endocrine cells in the gastric mucosa. Previous studies have shown that the proinflammatory cytokine interleukin (IL)-1β present during chronic gastritis inhibits histamine synthesis in ECL cells and leads to sustained functional impairment. This study investigated the effects of IL-1β on ECL cell apoptosis and the related signal-transduction mechanisms. Methods: ECL cells were isolated by pronase digestion and a combination of elutriation, gradient centrifugation, and 48-hour culture (purity ≥90%). Apoptosis was measured by terminal deoxynucleotidyl transferase–mediated deoxyuridine triphosphate nick-end labeling reaction and cell death detection enzyme-linked immunosorbent assay. Results: IL-1β (100 pg/mL) increased the rate of programmed cell death 2–3 fold in ECL cells after 24 hours of incubation (total of 12%–14%). This effect was completely inhibited by the NF-κB inhibitor, proteasome inhibitor I, and the nitric oxide synthase inhibitor (iNOS) N G -monomethyl-L-arginine (10 −4 mol/L), but not by the caspase 3 inhibitor, Asp-Glu-Val-Asp-CHO. Western blot analysis, reverse-transcription polymerase chain reaction (PCR), and in situ PCR showed that IL-1β induced gene expression (after 2–4 hours) and protein synthesis (6–18 hours) of the iNOS isoform in ECL cells. Bax protein expression was increased in response to IL-1β. In contrast, bcl-2 gene expression was increased in response to basic fibroblast growth factor, which has been shown to counteract IL-1β– induced apoptosis. Conclusions: These data suggest that IL-1β induces programmed cell death in isolated rat ECL cells via activation of NF-κB, iNOS, and the Bax protein. GASTROENTEROLOGY 2000;118:515-524

Multiple gastric carcinoids are a well-recognized complication of hypergastrinemia associated with chronic atrophic gastritis. However, the management of large tumors (>2 cm in diameter) remains uncertain, with the decision between antrectomy or total gastrectomy being empirical. This report describes the investigation of a patient with chronic atrophic gastritis and multiple large gastric carcinoid tumors. Before surgery, octreotide was infused for 72 hours to suppress enterochromaffin-like (ECL) cell and gastrin cell function. The infusion decreased plasma gastrin and gastrin synthesis; moreover, there were marked reductions in markers of ECL cell function, e.g., histidine decarboxylase and chromogranin A messenger RNA abundance, in carcinoid tumor tissue and macroscopically normal corpus mucosa. An antrectomy was performed, after which the patient made an uneventful recovery. Six months after surgery, a single residual polyp, enriched with smooth muscle cells but not ECL cells, was removed. One year after antrectomy, the remaining stomach was normal. The response of ECL cell markers in carcinoid tissue to octreotide suggested that these cells were under neuroendocrine control and, therefore, predicted a beneficial outcome for antrectomy. It is suggested that an octreotide supression test coupled with assay of histidine decarboxylase or chromogranin A gene expression is useful in the assessment of gastric carcinoid tumors.

Background & Aims: The effect of gastrin on the enterochromaffin-like cells in the rat stomach is mediated by cholecystokinin (CCK)-B receptors and manifested as activation of histidine decarboxylase (HDC). The dipeptoids PD 136450, PD 135158, and PD 134308 are thought to be selective CCK-B receptor antagonists. The effects of the dipeptoids and of gastrin-17 and sulfated CCK-8 on rat stomach HDC activity were examined. Methods: Drugs were infused intravenously or subcutaneously to fasted rats, and the HDC activity was determined. Results: The dipeptoids activated HDC with maximal responses (50%–60% of the maximal response to gastrin) at 1 μmol · kg −1 · h −1 . Rat gastrin-17 activated HDC maximally at 3 nmol · kg −1 · h −1 , and sulfated CCK-8 produced maximal response at 20 nmol · kg −1 · h −1 . The CCK-B receptor antagonist l-365,260 inhibited the HDC activation induced by gastrin, sulfated CCK-8, or the dipeptoids. The dipeptoids did not inhibit the gastrin-induced HDC activation. Conclusions: Gastrin, sulfated CCK-8, and the dipeptoids activated rat stomach HDC. l-365,260 but not devazepide inhibited the HDC activation. Thus, the dipeptoids, which failed to inhibit the gastrin-induced HDC activation, act as CCK-B receptor agonists and not as antagonists. It is important to recognize this to ensure appropriate interpretation of data obtained with these drugs.

Background/Aims: In the gastric mucosa of Helicobacter pylori -infected subjects, we previously detected N α -methyl histamine ( N α -MeHA), a minor catabolite of histamine and a potent agonist of histamine H 3 receptors. The origin of N α -MeHA and its effects on gastric histamine and somatostatin in infected subjects were investigated. Methods: Ten noninfected patients and 13 patients with intense colonization were compared. N α -MeHA content and its synthetic enzyme activity, N α -histamine methyltransferase, binding of [ 3 H] N α -MeHA, histamine and somatostatin contents, and histidine decarboxylase activity were assayed in antral and fundic biopsy specimens and in cultured H. pylori strains. Results: Gastric histamine and somatostatin contents as well as histidine decarboxylase activity were decreased in infected patients and were restored to normal after antimicrobial treatment. Both N α -MeHA and N α -histamine methyltransferase activity were present in the mucosa of infected patients and in cultured strains and were very low in noninfected patients or after eradication of H. pylori . [ 3 H] N α -MeHA bound to gastric mucosa but not to cultured strains. The [ 3 H] N α -MeHA specific binding sites were characterized as H 3 receptors. The amount of bound [ 3 H] N α -MeHA seemed correlated positively with somatostatin content and histidine decarboxylase activity and negatively with N α -MeHA content and N α -histamine methyltransferase activity. Conclusions: H. pylori is the main source of gastric N α -MeHA that may lower histidine decarboxylase activity and somatostatin content through H 3 receptors.

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 historically 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.

Background & Aims Elemental diet (ED) is effective for human Crohn's disease (CD). Although some of this effectiveness may be due to its low antigenic load and low fat content, the mechanisms remain unclear. We sought to assess the role of histidine, one of the constituent amino acids of ED, in controlling colitis. Methods The interleukin (IL)-10-deficient (IL-10 −/− ) cell transfer model of colitis was used. SCID mice with colitis induced by transfer of IL-10 −/− cells were maintained on experimented diets containing either single amino acids or a mixture. The severity of colitis was assessed by wet colon weight. Colonic tumor necrosis factor (TNF)-α messenger RNA (mRNA) expression was detected by quantitative reverse-transcription polymerase chain reaction. Mouse peritoneal macrophages were stimulated by lipopolysaccharides (LPS), with or without amino acids. The concentration of cytokines in the supernatant was determined by enzyme-linked immunosorbent assay. Inhibitor of nuclear factor (NF)-κB-α and nuclear p65 were confirmed by immunoblotting. Results In the IL-10 −/− transfer model, dietary histidine, but not alanine, reduced histologic damage and colon weight and TNF-α mRNA expression. Histidine inhibited LPS-induced TNF-α and IL-6 production by mouse macrophages in a concentration-dependent manner, whereas alanine or histidine-related metabolites had no such effect. Histidine inhibited LPS-induced NF-κB in macrophages. Conclusions These results showed that histidine could be a novel therapeutic agent for CD by inhibition of NF-κB activation, following down-regulation of proinflammatory cytokine production by macrophages. Thus, our studies provided new insights into the roles of amino acid metabolism in the pathophysiology of CD and for therapeutic strategies.

The enterochromaffinlike cells in the rat stomach are rich in histamine and are thought to be under the influence of gastrin. The effect of sustained endogenous and exogenous hypergastrinemia on the activity and proliferation rate of the enterochromaffinlike cells was studied by determining the histidine decarboxylase activity and histamine concentration and by combining histamine immunocytochemistry and autoradiography after in vivo labeling with [3H]thymidine. The proliferation rate of the stem cells in the oxyntic mucosal progenitor zone was also studied. Exogenous hypergastrinemia was induced by infusion of rat gastrin-17 (60 nmol.kg-1.day-1). Endogenous hypergastrinemia was induced by inhibition of gastric acid secretion with omeprazole (80 mumol.kg-1.day-1) or ranitidine (1200 mumol.kg-1.day-1). The effect of omeprazole was also studied in antrectomized rats. In intact rats, all treatments resulted in elevated plasma gastrin levels and were accompanied by an increase in the histidine decarboxylase activity and the histamine content of the oxyntic mucosa. This resulted in an increase in the enterochromaffinlike cell proliferation rate, leading to enterochromaffinlike cell hyperplasia. The number of labeled stem cells was increased, but this effect was not as pronounced as in the enterochromaffinlike cells. In antrectomized rats, the inhibition of acid secretion by omeprazole did not result in elevated plasma gastrin or in an increase in the activity or number of enterochromaffinlike cells, indicating that omeprazole per se had no effect on these cells. These data support the view that gastrin stimulates the proliferation rate of both enterochromaffinlike cells and stem cells. Gastrin also stimulates the activity of the enterochromaffinlike cells.

The histamine-storing enterochromaffinlike cells, which are numerous in the oxyntic mucosa of the rat stomach, are known to proliferate in response to long-lasting hypergastrinaemia. In addition, portacaval shunting, which is not associated with elevated serum gastrin, causes an increase in enterochromaffinlike cell density. The present study shows that the combination of portacaval shunting and omeprazole-evoked, long-lasting hypergastrinemia results in enhanced enterochromaffinlike cell hyperplasia despite the fact that the hypergastrinemia was not significantly greater than in intact omeprazole-treated rats. The mechanism behind the enhanced response to gastrin of the enterochromaffinlike cells in rats with portacaval shunts is unknown. When results from untreated and omeprazole-treated rats were plotted, there was a linear correlation between the serum gastrin concentration and the enterochromaffinlike cell density in both sham-operated rats and rats with portacaval shunts. We conclude that gastrin plays a role in the development of enterochromaffinlike cell hyperplasia following omeprazole treatment in rats with portacaval shunts but that other as yet unidentified agents may also promote the response.

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.

This report describes the trophic effects of exogenous gastrin on the digestive tract and pancreas and the effect on the density of enterochromaffinlike cells in the oxyntic mucosa of the stomach. Female rats were given 1.2 or 2.4 nmol/kg.h of synthetic human [Leu15]-gastrin-17 for 28 days (via osmotic minipumps implanted subcutaneously). As a result, measurable plasma gastrin increased from about 230 pg/ml in the controls to about 500 and 800 pg/ml in the low- and high-dose groups, respectively. The trophic effects of gastrin were reflected in increased stomach weight and oxyntic mucosal mass. Gastrin also increased the enterochromaffinlike cell density and associated parameters (histamine concentration and histidine decarboxylase activity) but was without demonstrable effects on other parts of the digestive tract and pancreas. The results show that continuous infusion of exogenous gastrin for 28 days induces trophic changes similar to those seen after a period of hypergastrinemia induced by treatment with effective inhibitors of acid secretion.

Background: Somatostatin (SS) inhibits both basal and gastrin stimulated histamine release from ECL cells in gastric mucosa. This is mediated through the SSTR2 receptor in human and rat antral mucosal strips. Histidine decarboxylase (HDC) is the enzyme responsible for histamine production in ECL cells and has previously been shown to be transcriptionally regulated through a gastrin response element. We postulated that SS may regulate the HDC promoter. The mechanisms through which SS may alter HDC transcription have not been elucidated. Methods: AGS-B cells were transfected with a plasmid containing 1.8 kb of the 5' promoter region of hHDC upsteam of the firefly luciferase reporter (1.8 kb hHDC-luc). Plasmids containing the cDNA of either human or rat SSTR2 were co-transfected. The cells were stimulated with 10 -7 M of gastrin, phothol ester (PMA) and dose responses with SS or octreotide were done. In addition overexpression of phosphatase SHP-1 and the G protein subunits Gictl and Gict3 were done using plasmids with the respective cDNA. Results.: Overexpression of both human and rat SSTR2 resulted in a dose dependent inhibition of hHDC transcription as measured by a luminometer. Maximal inhibition caused a 80% reduction in HDC transcription. This was seen in basal conditions, as well as with gastrin and PMA stimulated cells. Co-transfection with SHP-1 or its mutant did not block this effect. This inhibitory effect was not overcome with the phosphatase inhibitors sodium orthovanadate or okadaic acid. Addition of receptor agonists SS or octreotide resulted in a dose dependent 2-3 fold stimulation of HDC-Iuc activity. SS mediated stimulation in stably transfected cells was not altered by overexpression of GiQtl and Gia 3, suggesting that this paradoxical effect was not due to a lack of these subunits in AGS-B cells. Conclusions: SSTR2 has an inhibitory effect on HDC transcription in basal and stimulated AGS-B cells. This inhibition by the receptor is not mediated through a phosphatase pathway. Addition of agonists SS and octreotide produces a dose dependent stimulation in transcription of HDC. This is not due to a lack of the appropiate G i subunits in AGS-B cells. SS stimulates HDC transcription independently of G i pathway in AGS-B cells.

Gastrin acts via cholecystokinin-B/gastrin receptors to control histamine- and chromogranin A-producing ECL cells, which constitute the quantitatively predominant endocrine cell population in the acid-producing part of the rat stomach. Cholecystokinin-B receptor blockade is known to suppress the activity of ECL cells and to prevent their ability to respond to gastrin stimulation. The present study examines the reversibility of long-standing cholecystokinin-B receptor blockade of ECL cells. YM022, a potent and selective cholecystokinin-B receptor antagonist, was administered in a maximally effective dose by continuous subcutaneous infusion for 4 weeks (via osmotic minipumps). The resulting receptor blockade was manifested in elevated serum gastrin concentration (due to the ensuing acid inhibition), while the serum pancreastatin concentration, oxyntic mucosal histidine decarboxylase activity, histidine decarboxylase- and chromogranin A- mRNA levels and histamine and pancreastatin concentrations were lowered. After withdrawal of YM022, all these parameters returned to normal after varying lengths of time. The serum gastrin concentration and the oxyntic mucosal histidine decarboxylase activity returned to normal within a week after termination of treatment. The serum pancreastatin concentration and the mucosal histidine decarboxylase- and chromogranin A-mRNA levels returned to normal within 2 weeks of drug withdrawal. The mucosal pancreastatin and histamine concentrations remained unchanged for about a week before gradually returning to control levels within the next two weeks. Hence, the various effects of cholecystokinin-B receptor blockade of the ECL cells are fully reversible within 1-3 weeks of drug withdrawal.

BACKGROUND & AIMS. Raised plasma gastrin secondary to achlorhydria is associated with increased expression of several genes in ECL cells, notably histidine decarboxylase (HDC) and vesicular monoamine transporter type 2 (VMAT2). It is not clear whether endogenous gastrin regulates expression of these genes when gastric acid secretion is uninhibited. We have examined expression of these genes in ECL cells in INS-GAS transgenic mice that express the coding sequence of the human gastrin gene in pancreatic 13-cells and in which parietal cell function is uninhibited. METHODS. Plasma gastrin was measured by radioimmunoassay using antibody L2 (COOH-terminal specific for amidated gastrins) and L6 (specific for human G17). Gastrin release from 13-cells was stimulated by oral glucose. ECL cell function was assessed by Northem analysis of HDC and VMAT2 mRNAs. RESULTS. In INS-GAS mice fasted for 6hr, plasma human G17 was 67-+ 11 pM. When fasted mice were then allowed access to 20% glucose, plasma human G17 significantly increased (30min, 242 ± 33; 120min, 133 _+ 19 pM; n = 6; both p

Enriched preparations of intact histamine-containing cells were obtained from rat stomach by enzymatic digestion and density-gradient separation techniques. The distribution of histamine in the various density-gradient fractions was highly correlated with that for both histidine decarboxylase and DOPA-decarboxylase. The fractions with the highest content of these substances (density about 1.040) contained 8%–12% of cells which by electron microscopy had the characteristic appearance of an enterochromaffinlike cell. The distribution of these cells in the density gradient appeared to correlate with the distribution of histamine. The gastric histamine cells differed from the rat peritoneal mast cells in that they possessed neither serotonin nor receptors for IgE and did not release histamine upon exposure to compound 4880. The rat peritoneal mast cell, on the other hand, had high histamine (17 pg/ cell) and serotonin (0.6 pg/cell) contents but lesser amounts of soluble histidine decarboxylase and little DOPA-decarboxylase activity. These studies provide further evidence that in rat gastric mucosal histamine is stored in a cell having the morphologic and biochemical characteristics of an endocrinelike cell and the ability to take up and decarboxylate biogenic amines.

In intact rats plasma gastrin levels were increased during a 20-wk treatment course with either omeprazole or ranitidine. Although plasma gastrin levels were the same during treatment, the enterochromaffinlike (ECL) cell density increased approximately linearly with time at a rate correlated to the plasma gastrin level. Antrectomy prevented the ECL cell hyperplasia seen in omeprazole-treated rats, suggesting that it was not caused by omeprazole per se. Changes in ECL cell density roughly paralleled changes in oxyntic mucosal histidine decarboxylase activity and histamine concentration. Treatment with omeprazole also raised stomach weight and antral gastrin and gastrin cell density, reduced antral somatostatin cell density, but did not affect enterochromaffin cell density. Within 19 days of cessation of a 10-wk treatment course, plasma gastrin levels, oxyntic mucosal histidine decarboxylase activity, and antral gastrin and somatostatin cell densities had returned to control levels. The stomach weight was normal within 5–10 wk, antral gastrin concentration within 10 wk, and oxyntic mucosal ECL cell density and histamine concentration within 20 wk. After renewed treatment with omeprazole for 10 wk starting 10 wk after completion of the first omeprazole treatment period, changes in all parameters were of similar magnitude in animals previously treated with omeprazole and those previously treated with vehicle. The results suggest that the effects described are reversible and that gastrin cells turn over more rapidly than ECL cells.

Unoperated female rats were subjected to daily oral treatment with omeprazole (10 or 400 mumol/kg body wt), ranitidine (175 + 175 + 350 mumol/kg body wt), or vehicle and antrectomized rats were treated with omeprazole (400 mumol/kg body wt) or vehicle. After 10 wk of treatment, plasma gastrin levels were high in unoperated rats treated with the high omeprazole dose and with ranitidine, and low in antrectomized controls. Plasma gastrin levels were slightly higher in the low-dose omeprazole group than in the intact controls. In antrectomized rats treated with the high dose of omeprazole, the plasma gastrin level was in the same range as in intact control rats. A close correlation (r = 0.89, p less than 0.0001) was found between the plasma gastrin level and the oxyntic mucosal enterochromaffinlike cell density (as well as the tissue levels of histidine decarboxylase and histamine in the oxyntic mucosa) in all groups. The somatostatin cell density in the oxyntic mucosa was not altered by the various treatments. During a recovery period of 10 wk after the 10-wk treatment, the enterochromaffinlike cell density and histamine concentration decreased by 30%-40% in the rats treated with the high dose of omeprazole, whereas the corresponding values increased by 50% and 40%, respectively, in the control rats. The difference between the two groups, however, was still statistically significant. Plasma gastrin levels and gastric histidine decarboxylase activity returned to control values during recovery. The results suggest that the observed changes in enterochromaffinlike cell density are related to the plasma gastrin levels and that they are reversible. it is concluded that neither omeprazole nor ranitidine per se is likely to induce proliferation of enterochromaffinlike cells.

Rat gastric oxyntic glands contain argyrophil "enterochromaffin-like" endocrine cells that synthesize and store histamine and also have APUD ability—they can take up exogenous l-5-hydroxytryptophan (5-HTP), can decarboxylate it to 5-hydroxytryptamine (5-HT, serotonin) by the enzyme DOPA-decarboxylase, and can store the amine. Previous cytochemical studies suggested that these cells correspond to both the ECL and A-like cells, the two predominant endocrine cells identified by electron microscopy (EM) in rat oxyntic glands. In a recent study, however, we demonstrated that the ECL but not the A-like cell exhibited APUD ability when rat gastric mucosa was incubated with H3-5-HTP and studied by EM radioautography. The purpose of the present study was to identify by EM radioautography the histamine-synthesizing endocrine cells in the rat stomach. Pieces of rat (male Sprague-Dawley) gastric mucosa were incubated in organ culture with l-H3-histidine (50 μCi, 1.8 × 10 −5 M) with and without inhibitors and were processed for LM and EM radioautography. H3-histidine labeled the ECL cells heavily but the A-like and other endocrine cells only lightly. The labeling of ECL cells was only modestly reduced by cycloheximide, an inhibitor of protein synthesis, whereas the labeling of A-like and other endocrine cells was almost abolished. In contrast, the labeling of ECL cells was markedly reduced by 4-bromo-3-hydroxybenzyloxyamine (NSD-1055), an inhibitor of histidine decarboxylase and DOPA decarboxylase, but was not appreciably affected by carbidopa, an inhibitor of only the DOPA decarboxylase. Incubations with H3-histamine (50 μCi, 0.9 × 10 −5 M) failed to label endocrine cells. Thus, this study demonstrates that the ECL but not the A-like cell is the histamine-synthesizing endocrine cell of the rat stomach.

The localization of histidine decarboxylase-like immunoreactive structures in the mucosal cells of the rat stomach was studied by the peroxidase-antiperoxidase method. At the light microscopic level, histidine decarboxylase-like immunoreactivity-containing cells were concentrated in the basal part of the oxyntic region, whereas in other areas no immunoreactive cells were seen. Ultrastructural study showed that reaction end products were diffusely distributed within the cytoplasm of the enterochromaffinlike cells but other cell types such as A cells, G cells, and enterochromaffin cells were not labeled. These findings suggest that enterochromaffinlike cells synthesize histamine.

Determinations were made of the quantitative histological distribution of histamine and histidine decarboxylase in the body of the glandular stomach of fed and 14-hr fasted rats subjected to pyloroplasty and to pyloroplasty with vagotomy for comparision with untreated rats. Pyloroplasty on fasted rats had no significant effect on the concentration of histamine which was localized predominately in the chief cell zone. However, the superimposed vagotomy was associated with some increase in the concentration. With the fed rats, the concentration was essentially unchanged from normal in either group of operated animals and it also was about the same as that in the normal fasted group. Histidine decarboxylase activity, which was also localized predominately in the chief cell zone, underwent an increase in concentration following pyloroplasty of the fasted rats; no additional effect was observed with added vagotomy. The higher concentration of the enzyme activity in the fed rats was markedly further elevated in both groups of operated animals but these groups did not differ significantly from one another. An explanation of the elevation of histidine decarboxylase activity following pyloroplasty requires further investigation, but the lack of effect of the superimposed vagotomy on the enzyme activity would appear to rule out direct vagal control as the sole factor in determining the enzyme function at this site.

Summary The stomachs of pylorus-ligated rats were filled with 154 mm NaCl or 100 mm acetic acid plus 54 mm NaCl. After various intervals, the stomach contents were removed and the amount of histamine present was determined by bioassay on the guinea pig ileum. Homogenates were made from some rat stomachs. These were centrifuged, and the supernatant fluids were used as preparations of the enzyme, histidine decarboxylase. The activity of the enzyme was determined by counting the 14 CO 2 evolved when 14 C-carboxyl histidine was incubated with the enzyme. This measurement was converted to the histamineforming capacity (HFC). Acetic acid damage released significant amounts of histamine into the gastric contents. Release was complete after 30 min of irrigation. After 15 min of irrigation the HFC of the rats treated with acetic acid was increased 3-fold and was twice that of the NaCl-treated controls. After 2 hr the HFC of damaged stomachs had increased 12-fold as compared with a 6-fold increase in the control animals. Rats were treated with the mast cell histamine depletor, compound 48/80, and their stomachs were filled with either NaCl or acetic acid. At the end of 30 min there was no histamine present in NaCl irrigation fluids and less than one-tenth the amount normally found in the contents of acetic acid damaged stomachs. Since the releasable histamine pool is exhausted within 30 min, 48/80 prevents histamine release, and the HFC remains high after release is complete, it is concluded that the mucosal mast cells are the source of the histamine. It is hypothesized that the histamine release triggers an adaptive increase in the HFC. The increased enzyme activity furnishes more histamine to the damaged mucosa. Since activity is high throughout injury, the elevated HFC may serve some function during later stages of damage.

Unoperated female rats were subjected to daily oral treatment with omeprazole (10 or 400 mumol/kg body wt), ranitidine (175 + 175 + 350 mumol/kg body wt), or vehicle and antrectomized rats were treated with omeprazole (400 mumol/kg body wt) or vehicle. After 10 wk of treatment, plasma gastrin levels were high in unoperated rats treated with the high omeprazole dose and with ranitidine, and low in antrectomized controls. Plasma gastrin levels were slightly higher in the low-dose omeprazole group than in the intact controls. In antrectomized rats treated with the high dose of omeprazole, the plasma gastrin level was in the same range as in intact control rats. A close correlation (r = 0.89, p less than 0.0001) was found between the plasma gastrin level and the oxyntic mucosal enterochromaffinlike cell density (as well as the tissue levels of histidine decarboxylase and histamine in the oxyntic mucosa) in all groups. The somatostatin cell density in the oxyntic mucosa was not altered by the various treatments. During a recovery period of 10 wk after the 10-wk treatment, the enterochromaffinlike cell density and histamine concentration decreased by 30%-40% in the rats treated with the high dose of omeprazole, whereas the corresponding values increased by 50% and 40%, respectively, in the control rats. The difference between the two groups, however, was still statistically significant. Plasma gastrin levels and gastric histidine decarboxylase activity returned to control values during recovery. The results suggest that the observed changes in enterochromaffinlike cell density are related to the plasma gastrin levels and that they are reversible. it is concluded that neither omeprazole nor ranitidine per se is likely to induce proliferation of enterochromaffinlike cells.

In intact rats plasma gastrin levels were increased during a 20-wk treatment course with either omeprazole or ranitidine. Although plasma gastrin levels were the same during treatment, the enterochromaffinlike (ECL) cell density increased approximately linearly with time at a rate correlated to the plasma gastrin level. Antrectomy prevented the ECL cell hyperplasia seen in omeprazole-treated rats, suggesting that it was not caused by omeprazole per se. Changes in ECL cell density roughly paralleled changes in oxyntic mucosal histidine carboxylase activity and histamine concentration. Treatment with omeprazole also raised stomach weight and antral gastrin and gastrin cell density, reduced antral somatostatin cell density, but did not affect enterochromaffin cell density. Within 19 days of cessation of a 10-wk treatment course, plasma gastrin levels, oxyntic mucosal histidine decarboxylase activity, and antral gastrin and somatostatin cell densities had returned to control levels. The stomach weight was normal within 5-10 wk, antral gastrin concentration within 10 wk, and oxyntic mucosal ECL cell density and histamine concentration within 20 wk. After renewed treatment with omeprazole for 10 wk starting 10 wk after completion of the first omeprazole treatment period, changes in all parameters were of similar magnitude in animals previously treated with omeprazole and those previously treated with vehicle. The results suggest that the effects described are reversible and that gastrin cells turn over more rapidly than ECL cells.

Enriched preparations of intact histamine-containing cells were obtained from rat stomach by enzymatic digestion and density-gradient separation techniques. The distribution of histamine in the various density-gradient fractions was highly correlated with that for both histidine decarboxylase and DOPA-decarboxylase. The fractions with the highest content of these substances (density about 1.040) contained 8%-12% of cells which by electron microscopy had the characteristic appearance of an enterochromaffinlike cell. The distribution of these cells in the density gradient appeared to correlate with the distribution of histamine. The gastric histamine cells differed from the rat peritoneal mast cells in that they possessed neither serotonin nor receptors for IgE and did not release histamine upon exposure to compound 48/80. The rat peritoneal mast cell, on the other hand, had high histamine (17 pg/cell) and serotonin (0.6 pg/cell) contents but lesser amounts of soluble histidine decarboxylase and little DOPA-decarboxylase activity. These studies provide further evidence that in rat gastric mucosal histamine is stored in a cell having the morphologic and biochemical characteristics of an endocrinelike cell and the ability to take up and decarboxylate biogenic amines.