Cellular localization of histamine and monoamines in the gastric mucosa of man

Expression of the Cholecystokinin-B Receptor in Neoplastic Gastric Cells

Gastric cancer is an important disease due to its high mortality. Despite the decline in frequency, most cases are discovered late in its course, and most of the cancer patients die within a few years of diagnosis. In addition to Helicobacter pylori gastritis, gastrin is considered an important factor in the development of this disease, and thus, cholecystokinin-B receptor (CCKBR) becomes of interest. The aim of our study was to explore whether CCKBR is expressed in stomach cancers. Thirty-seven tumors from 19 men and 18 women diagnosed with either adenocarcinoma or neuroendocrine neoplasm (NENs) were included in this study. The tumors were classified into 29 adenocarcinomas and eight NENs. Immunohistochemistry with antibodies against chromogranin A (CgA), synaptophysin and CCKBR, and in situ hybridization with probes against CgA, CCKBR and histidine decarboxylase were used to further explore these tumors. Thirty-three (89%) of the tumors expressed CCKBR protein, whereas only 20 (54%) of all tumors expressed CCKBR mRNA. Of the 20 tumors expressing CCKBR mRNA, eight were NENs and 12 were adenocarcinoma. The highest amount of CCKBR was expressed in NEN. Interestingly, a high degree of co-expression of CCKBR and CgA was observed when the two markers were examined together with in situ hybridization. In conclusion, we found that all eight NENs expressed CCKBR and neuroendocrine markers in a majority of tumor cells. The same markers were also expressed in a proportion of adenocarcinomas supporting the view that gastrin is important in the development of gastric cancer.

Does long-term profound inhibition of gastric acid secretion increase the risk of ECL cell-derived tumors in man?

OBJECTIVE

Since the description of ECL cell-derived tumors in rodents after long-term profound acid inhibition inducing hypergastrinemia, there has been concern that proton pump inhibitors (PPIs) could also do that in man. The recent description of a Spanish family with gastric ECL cell tumors at the age of about 30 years secondary to a defect in the proton pump due to mutation in the ATP4A gene clearly shows that hypergastrinemia alone also is sufficient to induce ECL cell neoplasia in man. The present review aims to evaluate the risk of gastric neoplasia secondary to gastric acid inhibition.

METHODS

Literature (MEDLINE) was searched for the role of the ECL cell in gastric carcinogenesis in animals and man in general and particularly secondary to long-term inhibition of acid secretion.

RESULTS

An important proportion of patients treated with PPI develops hypergastrinemia causing ECL cell hyperplasia and the first descriptions of ECL cell carcinoids secondary to PPI have been reported. The role of the ECL cell has hitherto been under estimated in gastric carcinogenesis in man where for instance the signet ring cell type of gastric carcinoma seems to originate from the ECL cell.

CONCLUSIONS

The first two of three steps in rodent ECL cell carcinogenesis (hyperplasia, carcinoid, and carcinoma) secondary to PPI dosing, have been described for man. It is every reason to believe that the final step, gastric carcinoma, will develop also in man. Clinical decisions should be based not only on so-called evidence based medicine, but also on physiological knowledge and animal studies.

Gastrointestinal hormone research - with a Scandinavian annotation

Gastrointestinal hormones are peptides released from neuroendocrine cells in the digestive tract. More than 30 hormone genes are currently known to be expressed in the gut, which makes it the largest hormone-producing organ in the body. Modern biology makes it feasible to conceive the hormones under five headings: The structural homology groups a majority of the hormones into nine families, each of which is assumed to originate from one ancestral gene. The individual hormone gene often has multiple phenotypes due to alternative splicing, tandem organization or differentiated posttranslational maturation of the prohormone. By a combination of these mechanisms, more than 100 different hormonally active peptides are released from the gut. Gut hormone genes are also widely expressed outside the gut, some only in extraintestinal endocrine cells and cerebral or peripheral neurons but others also in other cell types. The extraintestinal cells may release different bioactive fragments of the same prohormone due to cell-specific processing pathways. Moreover, endocrine cells, neurons, cancer cells and, for instance, spermatozoa secrete gut peptides in different ways, so the same peptide may act as a blood-borne hormone, a neurotransmitter, a local growth factor or a fertility factor. The targets of gastrointestinal hormones are specific G-protein-coupled receptors that are expressed in the cell membranes also outside the digestive tract. Thus, gut hormones not only regulate digestive functions, but also constitute regulatory systems operating in the whole organism. This overview of gut hormone biology is supplemented with an annotation on some Scandinavian contributions to gastrointestinal hormone research.

Upper gastrointestinal physiology and diseases

Nordic research on physiology and pathophysiology of the upper gastrointestinal tract has flourished during the last 50 years. Swedish surgeons and physiologists were in the frontline of research on the regulation of gastric acid secretion. This research finally led to the development of omeprazole, the first proton pump inhibitor. When Swedish physiologists developed methods allowing the assessment of acid secretion in isolated oxyntic glands and isolated parietal cells, the understanding of mechanisms by which gastric acid secretion is regulated took a great step forward. Similarly, in Trondheim, Norway, the acid producing isolated rat stomach model combined with a sensitive and specific method for determination of histamine made it possible to evaluate this regulation qualitatively as well as quantitatively. In Lund, Sweden, the identification of the enterochromaffin-like cell as the cell taking part in the regulation of acid secretion by producing and releasing histamine was of fundamental importance both physiologically and clinically. Jorpes and Mutt established a center at Karolinska Institutet in Stockholm for the purification of gastrointestinal hormones in the 1960s, and Danes followed up this work by excelling in the field of determination and assessment of biological role of gastrointestinal hormones. A Finnish group was for a long period in the forefront of research on gastritis, and the authors' own studies on the classification of gastric cancer and the role of gastrin in the development of gastric neoplasia are of importance. It can, accordingly, be concluded that Nordic researchers have been central in the research on area of the upper gastrointestinal physiology and diseases.

Neuroendocrine pathology of the stomach: the Parma contribution

The current knowledge on gastric neuroendocrine pathology essentially developed in the last four decades. The historical evolution of the concepts and of the relevant clinical implications is described from the perspective of a group actively participating in this research domain. The histamine-producing enterochromaffin-like (ECL) cells have been recognized as the leading cell type involved in the most significant alterations of gastric neuroendocrine cells. The trophic stimulus exerted by circulating gastrin has been demonstrated to have a crucial role on proliferative changes of ECL cells through a sequence of hyperplasia-dysplasia-neoplasia described by Solcia et al. (Digestion 41:185-200,1988). The development of ECL cell tumors in rats treated with toxicological doses of inhibitors of gastric acid secretion prompted appropriate anatomoclinical investigations proving the lack of tumor risk in humans when therapeutic dosages of the drugs are used. Moving from the comprehensive concept of gastric carcinoid, different types of neuroendocrine tumors have been identified in the stomach with substantial variations in prognosis and treatment options. In general, ECL cell tumors developed in hypergastrinemic conditions were found to behave better than those originating outside the setting of hormonal stimulation. Pathological features highly predictive of patient survival have been described. The genetic changes involved in tumor development and progression have revealed substantial overlapping with those of neuroendocrine tumors of other foregut derivatives (i.e., pancreas, duodenum, lung) delineating a family of neuroendocrine tumors genetically distinct from those of the distal parts of the digestive system.

The regulation of gastric acid secretion - clinical perspectives

The purpose of this review, based upon 40 years of research, is to clear old controversies. The gastric juice is a strong acid with active enzymes (pepsin and lipase); ideal for killing swallowed microorganisms. Totally isolated rat stomach and histamine determination. Human gastric carcinomas were examined for ECL cell differentiation because tumours found in rodents after dosing with inhibitors of acid secretion were reclassified to be of ECL cell origin. The gastrin receptor is localized to the ECL cell only, where gastrin stimulates the function and growth. Drug-induced hypo-acidity induces hypergastrinaemia and ECL cell hyperplasia responsible for rebound acid hypersecretion. Every condition with long-term hypergastrinaemia disposes to ECL cell neoplasia. In man, both atrophic gastritis and gastrinoma lead to ECL cell carcinoids. Proton pump inhibitors induce hypergastrinaemia with ECL cell hyperplasia and ECL cell carcinoids that disappear when stopping treatment. The gastrin antagonist netazepide induces regression of ECL cell carcinoids due to atrophic gastritis. Human gastric carcinomas of diffuse type, particularly the signet-ring subtype, show ECL cell differentiation, suggesting involvement of gastrin in the carcinogenesis. Helicobacter pylori (Hp) causes gastritis and peptic ulcer, and when infecting the antrum only gives a slight hypergastrinaemia with acid hypersecretion predisposing to duodenal ulcer, but protecting from gastric cancer. When Hp infection spreads to oxyntic mucosa, it induces atrophy, reduced acid secretion and marked hypergastrinaemia and cancer.It is remarkable that the interaction between Hp and gastrin may explain the pathogenesis of most diseases in the upper gastrointestinal tract.

Antisera against rat recombinant histidine decarboxylase: immunocytochemical studies in different species

Histamine is involved in many important biological processes such as allergic reactions, gastric acid secretion and neurotransmission. The formation of histamine is catalysed by the enzyme histidine decarboxylase. In order to understand the role of histamine in different tissues, information about the cellular localisation of the decarboxylase is important. However, the availability of antisera against the enzyme, which can be used in immunocytochemical techniques, has so far been limited, mainly due to the difficulties in purifying sufficient amounts of histidine decarboxylase from various tissues. In the present study we describe the use of antisera raised against rat recombinant histidine decarboxylase to localise the enzyme immunocytochemically in the gastric mucosa of different mammals and submammalian vertebrates. The antisera specifically stained histidine decarboxylase-immunoreactive cells in the gastric mucosa of not only rat, but also of species like frog, chicken, mouse and dog. This is the first report describing the immunocytochemical distribution of the decarboxylase in the gastric mucosa of species other than rat. These antisera are likely to become valuable tools for further studies of the immunocytochemical localisation of histidine decarboxylase.

The opioid peptide DAMME modulates histamine's content in gastric mucosa of the rat

The effects of a synthetic Met-enkephalin analogue D-Ala2, MePhe4Met(O)5-ol]enkephalin (DAMME) (1 mg/kg. IP) on gastric damage produced by necrotizing agents (0.6 N HCl, ethanol 1 ml/rat, PO) were evaluated, and the correlation between histamine and opioids in stomach was investigated, Rats pretreated with DAMME bad significantly less severe lesions and lower histamine content in gastric tissue. The histamine level, expressed in mg/g of gastric tissue, changed from 0.41 +/- 0.10 of control animals to 1.33 +/- 0.12 for HCl and 1.51 +/- 0.20 for ethanol treatment, whereas in animals pretreated with DAMME the values were significantly reduced to 0.55 +/- 0.13 and 0.65 +/- 0.15. These results confirm a link between the gastroprotection produced by opioids and the modulation of histaminergic activity in the rat stomach.

Review article: the use of gastric acid-inhibitory drugs--physiological and pathophysiological considerations

All vertebrates secrete gastric acid. Acid denatures the proteins in the food and thus makes them more accessible to proteolytic enzymes, and it kills swallowed micro-organisms. Gastric acid plays an important pathogenetic role in peptic ulcer disease and reflux oesophagitis. In these diseases, drugs that inhibit secretion of gastric acid will heal the lesions and suppress the symptoms. However, both reflux oesophagitis and peptic ulcer tend to recur when the acid-inhibitory treatment is stopped. Therefore, these patients often require long-term treatment with acid-inhibitors. In this overview the potential risks of long-term profound inhibition of acid secretion, raising the pH above 4 for a considerable time, resulting in reduced killing of micro-organisms and secondary hypergastrinaemia, are discussed. Gastrin regulates both the function (production and release of histamine) and growth of the enterochromaffin-like (ECL) cell. Hitherto, the role that this cell plays in gastric carcinogenesis appears to have been underestimated.

The enterochromaffin-like (ECL) cell. Physiological and pathophysiological role

Histamine has a central role in the regulation of gastric acid secretion. This histamine is produced by and released from the enterochromaffin-like (ECL) cell which accordingly has a key-regulatory role in the oxyntic mucosa. Gastrin and the vagal nerves stimulate the formation and release of histamine from the ECL cell. Moreover, gastrin and the vagal nerves also stimulate the proliferation of the ECL cell. An increased ECL cell density may partly explain the increased acid secretion in patients with duodenal ulcer, particularly in patients with Zollinger-Ellison syndrome. The reduced potency of histamine-2 blockers in patients with Zollinger-Ellison syndrome is probably due to increased histamine release by an elevated ECL cell mass. Prolonged and profound hypergastrinemia may lead to ECLomas. Moreover, a proportion of diffuse gastric carcinomas may originate from ECL cells.

The role of gastric secretagogues in regulating gastric histamine release in vivo

The effect of short-term intragastric arterial infusion of pentagastrin and methacholine on histamine and N tau-methyl histamine secretory rates was evaluated in mongrel dogs in vivo. Doses of pentagastrin and methacholine were chosen that stimulate gastric acid secretion equivalently. Histamine and N tau-methyl histamine secretory rates were evaluated by measuring the arterial and gastric venous plasma histamine and N tau-methyl histamine concentrations at several time points during the secretagogue infusion, and gastric blood flow was continuously monitored. Histamine and N tau-methyl histamine plasma concentrations were analyzed by stable isotope dilution technique using gas chromatography/negative ion-chemical ionization mass spectrometry. Histamine and N tau-methyl histamine secretory rates were calculated by subtracting the arterial from the venous plasma concentrations and multiplying the difference by gastric plasma flow. Infusion of pentagastrin resulted in large pulsed increase of histamine release from 1.5 +/- 0.7 ng/min at time 0 to 72 +/- 20 ng/min at 5 minutes, which decreased to a plateau of 20 +/- 8 ng/min at 20 minutes. N tau-Methyl histamine secretory rate increased from 6.7 +/- 1.9 ng/min at baseline to a maximum of 42.5 +/- 13.1 ng/min at 10 minutes, and the increase was maintained for the duration of the pentagastrin infusion. Methacholine infusion was associated with a small but sustained increase in histamine release, from a baseline of 1.6 +/- 0.6 ng/min to 5.9 +/- 1.7 ng/min at 5 minutes. N tau-Methyl histamine secretory rate was unchanged by methacholine. Gastric blood flow changes to pentagastrin roughly paralleled the extent of histamine release, but methacholine is a gastric vasodilator in its own right. Our data indicate that pentagastrin is a much more effective stimulator of gastric histamine release than methacholine and that the overall role of histamine in gastrin-stimulated acid output is likely to be different from the role of histamine in cholinergic-mediated gastric acid output.

Marked increase in gastric histidine decarboxylase activity in patients with hypergastrinemia

Histidine decarboxylase (HDC) activity and histamine content were measured in endoscopic gastric biopsy specimens of 19 control subjects with normogastrinemia and 6 patients with hypergastrinemia. In controls, the HDC activity was 3 fold higher in fundic mucosa (120 +/- 13 fmol/min/mg protein, mean +/- S.E.) than in antral mucosa (39 +/- 5 fmol/min/mg protein). In patients with hypergastrinemia, an extremely high HDC activity (713 +/- 181 fmol/min/mg protein) was observed in fundic mucosa, although the HDC activity in antral mucosa was not significantly different from that of controls. The histamine content in fundic mucosa was also significantly higher in patients with hypergastrinemia than in controls but no significant difference was seen in histamine content in antral mucosa between the two groups. These results are compatible with the hypothesis that in man, as well as in rat, histamine synthesis in fundic mucosa is enhanced by gastrin.

Mucosal mast cells in reflux gastritis and chronic (type B) gastritis

The histological features that characterize alkaline reflux gastritis are typical of the histamine-mediated response to tissue injury. We have investigated this in nine patients with symptomatic reflux gastritis following partial gastrectomy for duodenal ulcer by determining the gastric mucosal mast cell count before and after Roux-en-Y biliary diversion. Following diversion, the histological picture changed from that of reflux gastritis to type B chronic gastritis in all cases. The mean mucosal mast cell count in all patients was 47.57/mm2 before diversion and 123.33/mm2 after diversion (P less than 0.05). Analysis of the paired data, in which eight out of nine patients showed a rise in mucosal mast cell numbers following bile diversion, also showed a significant difference before and after surgery (P less than 0.01). The gastric mucosal mast cell count is significantly less in reflux gastritis than in type B chronic gastritis. This is most likely to be due to increased degranulation, which would explain why striking vascular changes occur in the absence of inflammatory cell infiltration in reflux gastritis.

Circulating gastrin, endocrine cells, histamine content, and histidine decarboxylase activity in atrophic gastritis

Thirty-five patients with fundic atrophic gastritis and achlorhydria were classified in two groups according to the presence or absence of fundic argyrophil, mostly enterochromaffinlike cell hyperplasia. Among the biologic and histologic parameters studied, the hyperplasic group differed only by a circulating hypergastrinemia and an antral G-cell hyperplasia. The histamine content, the histidine decarboxylase activity, and the mast cell number of fundic biopsies were determined in 10 controls, 16 of the preceding patients (11 with and 5 without fundic argyrophil-cell hyperplasia), and 5 patients with fundic atrophic gastritis and neither achlorhydria nor hyperplasia. Histamine content and histidine decarboxylase activity were increased only in the hyperplasic group despite an unchanged mast cell number. For all fundic biopsies the argyrophil-cell density was positively related to the histamine content. Finally, the argyrophil-cell hyperplasia occurring in fundic atrophic gastritis with achlorhydria is associated not with the gastritis intensity, as assessed by histologic and secretory criteria, but with a circulating hypergastrinemia and an increase of both fundic histamine content and histidine decarboxylase activity.

A double-blind crossover study of the effect of a chromone carboxylic acid, FPL 52694, on overnight fasting gastric acid secretion

The chromone FPL 52694 is a preparation thought to act by stabilizing mast cell membranes, thus reducing free histamine in the gastric mucosa. The effect of FPL 52694 on overnight gastric secretion was tested in 15 dyspeptic individuals in a double-blind crossover study. Each individual received the chromone preparation or placebo for 1 week. After each of the treatment periods gastric secretion was collected after 6 h of fasting by continuous suction for 8 h during the night. A significant reduction of the total acid secretion was observed after active drug compared with placebo administration, mean reduction being 17% (median, 23%). No difference was observed between 30-min and 60-min periods. FPL 52694 had no significant effect on pepsin, intrinsic factor (IF) or volume secretion. The difference in the effect on pepsin and acid secretion, reflected in a significant increase in the pepsin to acid ratio, indicates that intrinsic histamine, similarly to extrinsic histamine, has a specific effect on parietal cells. The difference in effect on acid and IF secretion indicates that intrinsic histamine not only has a specific effect on parietal cells but also has different effects on the secretory substances contained in this cell. Since IF was not reduced by the use of FPL 52694, it may be that this substance will not influence vitamin B12 metabolism.

VIP and histamine H2 receptor activity in human fetal gastric glands

Vasoactive intestinal peptide (VIP, EC50 = 6.4 X 10(-10)M) and histamine (EC50 = 3 X 10(-6)M) activated the cyclic AMP generating system in gastric glands isolated from two human fetuses at 23 weeks gestation. Histamine antagonism by the H2 receptor blockers cimetidine (Ki = 0.35 X 10(-6)M) and ranitidine (ki = 0.51 X 10(-7)M) clearly characterized the histaminic activation as being of the H2 type. It is suggested that these two vasoactive hormones may operate as neurocrine/paracrine regulators of the differentiation and/or function of the human gastric mucosa in utero.

Histamine in endocrine cells in the stomach. A survey of several species using a panel of histamine antibodies

Antibodies to histamine were used to examine the localization of the amine in cells of the stomach and upper small intestine of a great variety of species, including cartilaginous and bony fish, amphibia, reptiles (lizard), birds (chicken) and a large number of mammals. In all species gastric histamine was localized in endocrine cells (invariably found in the epithelium) and mast cells (usually with an extra-epithelial localization). The endocrine cells were identified as such by immunostaining with antibodies to chromogranin A and the mast cells were identified by toluidine blue staining. Histamine-immunoreactive endocrine cells were found almost exclusively in the acid-producing part of the stomach; only rarely were such cells observed in the pyloric gland area. They were fairly numerous in the gastric mucosa of the two subclasses of fish as well as in the amphibia and reptile species studied. Here, the majority of the histamine-immunoreactive endocrine cells seemed to have contact with the gastric lumen (open type cells) and were located in the surface epithelium (certain fish only) or together with mucous neck cells at the bottom of the pits. In the chicken, histamine-immunoreactive endocrine cells were numerous and located peripherally in the deep compound glands. They were without contact with the lumen (closed type) and had long basal extensions ("paracrine" appearance), running close to the base of the oxyntic-peptic cells. In mammals, the number of histamine-immunoreactive endocrine cells in the stomach varied greatly. They were particularly numerous in the rat and notably few in the dog, monkey and man. In all mammals, the histamine-immunoreactive endocrine cells were of the closed type and located basally in the oxyntic glands. They often had a "paracrine" appearance with long basal processes. Histamine-storing mast cells, finally, were few in both subclasses of fish as well as in the amphibian species and in the lizard. They were fairly numerous in chicken proventriculus (beneath the surface epithelium), few in the oxyntic mucosa of mouse, rat and hamster, moderate in number in hedgehog, guinea-pig, rabbit, pig and monkey, and numerous in cat, dog and man.(ABSTRACT TRUNCATED AT 400 WORDS)

Two biochemically distinct populations of histaminocytes separated by isokinetic sedimentation of dispersed rat gastric cells

Two populations of histaminocytes, with different sedimentation rates (SR), were separated by a computer developed isokinetic gradient using dispersed rat gastric mucosal cells. Histamine content, histidine decarboxylase (HDC) activity and incorporation of radiolabelled histidine metabolites were used to assess the migration of specific cells throughout the gradients. One histaminocyte population, with cells of lower SR, contained high HDC activity and undetectable levels of histamine, whereas the other population, with cells of higher SR, contained lower HDC activity and high concentration of histamine. Both types of histaminocytes incorporated 3H-histidine metabolites. Electron microscopy showed that the fractions containing histaminocytes with lower SR had 3.5 times more endocrine ECL cells than the original population of dispersed fundic cells and lacked A and D cells, whereas the fractions with histaminocytes of higher SR were associated with a 2.7 times higher concentration of A and D cells and with a 7.7 times higher ratio of a variety of partial cells with a distinct mitochondrial morphology. These results are consistent with prior novel information regarding the separation of two populations of rat histaminocytes using different sedimentation techniques.

Histofluorescent and radioenzymatic analysis of colonic catecholamines in man

Colonic tissues from patients with ulcerative colitis (UC), ileal tissue from patients with Crohn's disease (CD), and other ileocolonic disorders were radioenzymatically assayed for norepinephrine (NE) and dopamine (DA). These assays showed that the NE content of UC colon ranged from 3.2 to 4.3 ng/mg wet tissue, while in other colonic disorders it ranged from 3.0 to 5.3 ng/mg. Similarly, the DA content of UC colon ranged from 0.42 to 1.17 ng/mg wet tissue, while for other colonic disorders it ranged from 0.48 to 0.89 ng/mg. The same tissues were examined histochemically using glyoxylic acid condensation of catecholamines (CA) for the semi-quantitation of CA-containing structures. Examination of these structures revealed an apparent increase in their staining intensity in the myenteric plexus in ulcerative colitis as compared to other colonic disorders. Morphologically, the CA-containing structures of the colon appeared to be increased in UC, but determination of the NE and DA concentrations in colonic samples revealed no statistically significant differences in comparable regions of the colon.

Gastrin receptors on isolated canine parietal cells

The receptors in the fundic mucosa that mediate gastrin stimulation of acid secretion have been studied. Synthetic human gastrin-17-I (G17) with a leucine substitution in the 15th position ( [Leu15]-G17) was iodinated by chloramine T; high saturable binding was found to enzyme-dispersed canine fundic mucosal cells. 127I-[Leu15]-G17, but not 127I-G17, retained binding potency and biological activity comparable with uniodinated G17. Fundic mucosal cells were separated by size by using an elutriator rotor, and specific 125I-[Leu-15]-G17 binding in the larger cell fractions was highly correlated with the distribution of parietal cells. There was, however, specific gastrin binding in the small cell fractions, not accounted for by parietal cells. Using sequential elutriation and stepwise density gradients, highly enriched parietal and chief cell fractions were prepared; 125I-[Leu15]-G17 binding correlated positively with the parietal cell (r = 0.98) and negatively with chief cell content (r = -0.96). In fractions enriched to 45-65% parietal cells, specific 125I-[Leu15]-G17 binding was rapid, reaching a steady state at 37 degrees C within 30 min. Dissociation was also rapid, with the rate similar after 100-fold dilution or dilution plus excess pentagastrin. At a tracer concentration from 10 to 30 pM, saturable binding was 7.8 +/- 0.8% per 10(6) cells (mean +/- SE) and binding in the presence of excess pentagastrin accounted for 11% of total binding. G17 and carboxyl terminal octapeptide of cholecystokinin (26-33) were equipotent in displacing tracer binding and in stimulating parietal cell function ( [14C]aminopyrine accumulation), whereas the tetrapeptide of gastrin (14-17) had a much lower potency. Proglumide inhibited gastrin binding and selectively inhibited gastrin stimulation of parietal cell function. Canine parietal cells have specific receptors for gastrin that mediate stimulation of parietal cell function. Gastrin receptors were undetectable on chief cells, and yet present on another smaller mucosal cell(s).

Separation and characteristics of two histaminocytes from rat gastric mucosa

To determine the properties of rat gastric cells involved in histamine metabolism (histaminocytes), fundic mucosa was enzymatically dispersed prior to separation by sedimentation methods. The distribution of histamine content, histidine decarboxylase (HDC) activity and incorporation of radioactive histidine metabolites were used to determine the characteristics of various populations of gastric cells. All activities measured, as well as most of the dispersed gastric cells, occurred in a narrow range of density between 1.083 and 1.091 g/ml. Velocity sedimentation showed that two populations of histaminocytes can be distinguished. One population has a higher sedimentation rate, suggesting a larger size, contains histamine, HDC activity and incorporates radioactive metabolites. Another population, in fractions with lower sedimentation rates, contains little histamine, has a higher HDC activity than the previous population and also incorporates radiolabelled histidine metabolites. For the first time, two populations of viable histaminocytes have been separated that differ in their biochemical properties.

The occurrence of serotonin-containing cells in the esophageal epithelium of the bullfrog Rana catesbeiana: a fluorescence histochemical and immunohistochemical study

Fluorescence histochemical examination of biogenic amines of the frog esophageal mucosa revealed that a serotonin-like monoamine exhibiting an yellow fluorescence was present in a certain type of cells. The new type of cells was specifically stained by the immunohistochemical method using anti-serotonin antiserum. From these observations, it is suggested that the new cell type in the esophageal mucosa probably contains 5-hydroxytryptamine (serotonin). The serotonin-containing cells were argentaffin, but negative for Grimelius' silver stain.

Immunocytochemistry of serotonin-containing nerves in the human gut

An immunocytochemical technique, using L-tryptophan enhancement and paraformaldehyde fixation, has been successfully applied for the demonstration of serotonin-containing neurons in the human enteric nervous system. Throughout the intestine, serotonin-immunoreactive nerves were mainly detected in the myenteric plexus and, to a smaller extent, in the submucous plexus, while hardly any nerve fibres were seen in the mucosa. This approach provides a useful tool for the investigation of neuropathological conditions of the gut.

A modified Schayer procedure for the estimation of histidine decarboxylase activity: its application on tissue extracts from gastric mucosa of various mammals

The question of whether the gastric mucosa of mammals other than rats, mice and hamsters contains an acid (specific) histidine decarboxylase was re-investigated by using a modification of the classical isotope dilution method of Schayer. Its reliability was tested regarding sensitivity, specificity, precision and accuracy, applying criteria recommended by the International Federation of Clinical Chemistry. The assay is now suitable for measuring rather large series of samples. The suitability of several blanks for detecting histidine decarboxylase activity was investigated as a special problem of accuracy. The semicarbazide blank was found to be as reliable as the heating blank, the blank with tissue extract pretreated with perchloric acid or an incubation mixture without radio-labelled histidine. Reaction kinetics of histamine formation were linear over an incubation period of at least 3 h. Histidine decarboxylase activity as a rather low pH and substrate concentration, which is characteristic for the acid (specific) histidine decarboxylase, was demonstrated inthe gastric mucosa of human subjects, dogs, rabbits and guinea-pigs, always using the same incubation conditions for all species investigated. The highest enzymic activity was present in the oxyntic mucosa, but could be measured also in other parts of the stomach.

Effect of cimetidine on the amounts of histamine in the gastric mucosa of patients with gastric or duodenal ulcers

Measurements were made of the amounts of histamine extracted from patients with peptic ulcer disease and control subjects suffering from various gastrointestinal diseases. Patients with duodenal ulcer, gastric ulcer, or recurrent duodenal ulcer after proximal gastric vagotomy often had less gastric mucosal histamine than did normal controls. Cimetidine therapy increased the amounts of the histamine to above control levels, presumably by suppression of output. It is concluded that endogenous amounts of histamine reflect the pathogenic states in the gastric mucosa of patients with peptic ulcer diseases. Cimetidine, as does vagotomy, increases the amount of gastric mucosal histamine. These findings suggest that the increase in mucosal histamine with cimetidine is not due to activation of histamine methyl transferase, but rather to suppression of histamine output into the gastric juice.

APUD cells and neuroepithelial bodies in hamster lung: methods, quantitation, and response to injury

A comparative study of the Falck-Hillarp Technique, a modification of Eaton-Fedde procedure and silver staining of aldehyde-fixed tissue was carried out to determine the most efficient procedure to demonstrate neuroendocrine cells of the hamster and rat lung. The modified Eaton-Fedde procedure is the most efficient method of observing these cells, and is also the easiest to perform. With this method, the normal hamster lung contains a total of 2.00 x 10(-1) to 3.00 x 10(-1) neuroendocrine cells/mm in the small and large bronchioles. In the larger airways approximately 3.51 x 10(-1) neuroepithelial bodies (NEB)/mm are observed. Immediately after 24-hour exposure to NO2 the number of APUD cells dropped to approximately 25% of the control levels. These cells were decreased to 50% of the control levels throughout the 28 days of exposure. The number of NEB decreased transiently after 24 hours of NO2 but returned to normal numbers by day 14. We recommend the application of fluorescence techniques coupled with standardised sections and quantitative methods of study for analysis of APUD cells and NEB.

Histamine and peptic ulcer: influence of sample-taking on the precision and accuracy of fluorometric histamine assay in biopsies of human gastric mucosa

From a methodological point of view the relevance of clinical-biochemical trials depends on the answers to mainly four complexes of questions: (1) the reliability of the assays in the clinical situation to be tested, (2) the precision and accuracy of sample-taking, (3) the qualification of the design and the protocols in the clinical part of the trial and (4) the usefulness of the time concepts in the trial concerning biorhythms, seasonal influences, psychological trauma of diagnostic procedures and treatment. In this study mainly the second complex of questions was studied intensely. The precision of the fluorometric histamine assay in biopsy specimens from human gastric mucosa depended on several conditions: Biochemical technique, sample preparation and removal of biopsies from gastric mucosa via endoscopy. The CV% of the whole procedure was about 8-times higher than that of the biochemical technique. In clinical-biochemical studies on the significance of histamine or any other hormone (such as gastrin) in any disease (uch as duodenal ulcer) it seems therefore useless to describe the precision of an assay only by the variance of the biochemical technique. Calculation of the histamine content as mean of 3 samples reduced the CV% from 27.2 to 14.9% and should therefore be recommended.

Histamine content and mast cells in human gastric and duodenal mucosa

A high histamine content was found in all areas of human gastric and duodenal mucosa. In single subjects there was no general preference of histamine being located predominantly in fundus and corpus. In biopsy specimens of human corpus mucosa many histamine-containing O-PD reactive cells could be identified. In the sections treated previously with O-PD also many toluidine blue staining cells (mast cells) could be visualized. As shown by a transcription technique their place and number was the same as those of O-PD reacting cells. It is concluded that histamine in human corpus mucosa is localized exclusively in mast cells which seem to participate in acid secretion and in duodenal ulcer disease in man.

Effect of selective gastric vagotomy on histamine concentration in gastric mucosa of patients with duodenal ulcer

In a prospective controlled trial, histamine concentrations in human gastric mucosa were determined fluorometrically in 23 patients 6–11 months after selective gastric vagotomy with drainage and in patients who had undergone other types of operation for duodenal ulcer. The study was in two parts: part 1, a synchronous investigation of mucosal histamine concentrations in patients who had undergone vagotomy, in duodenal ulcer patients before operation and in control subjects; part 2, a consecutive study of the same patients before and after vagotomy.

In part 1, patients with Hollander-negative vagotomy were found to have significantly higher mucosal histamine concentrations than ‘healthy’ control subjects or duodenal ulcer, however, had as low mucosal histamine concentrations as duodenal ulcer patients who had not been operated on. In part 2, all duodenal ulcer patients showed an increase in gastric mucosal histamine concentration after vagotomy (P < 0·01). The smallest increase was in a patient with an incomplete vagotomy. Control patients who were not operated on but who underwent endoscopy and biopsy twice in the period of investigation, did not show any increase in mucosal histamine concentration between the times of the first and the second biopsy. The overall results of selective vagotomy and drainage in this study, with respect both to clinical Visick gradings and to radiological and acid secretory findings, were comparable to those reported by other authors. No significant change in numbers of parietal cells was found after vagotomy. Thus, selective gastric vagotomy with a drainage procedure leads to increased concentrations of histamine in the mucosa of the body of the stomach in man. The mechanism is not clear, but might be through inhibition of histamine release from mast cell stores.

Endocrine-like cells of the pulmonary epithelium of the human adult lung

The morphological and histochemical characteristics of endocrine-like cells of the pulmonary epithelium of the right lower lobe of 12 human adult lungs were studied. Few cells were reactive to the argyrophil silver method of Grimelius and of Sevier and Munger and cells with a similar morphology and distribution emitted a green or yellow fluorescence after treatment of the lung epithelium with the amine presursors L-DOPA or L-HTP, respectively. A greater number of cells seems to be demonstrated by electron microscopy. The cells were characterized by small, round secretory granules showing a central dense core and a very thin clear halo between the core and the surrounding membrane. The cells are thought to be related to the endocrine-like cells of the pulmonary epithelium of the human foetal lung and to cells of carcinoids of larger bronchi.

Serotonin containing and histamine containing cells in human stomach. Identification of these cells by fluorescent microscope and electron microscope

Paraformaldehyde (PF) treatment of epithelial cells of human stomach revealed intense yellow fluorescent granules within the cells. These granules were identified as serotonin on microspectrofluorometry. Serotonin containing cells were also identified as enterochromaffin cells (EC cells) under electron microscope and by the histochemical analysis. O-phthalaldehyde treatment (OPT) of epithelial cells in human stomach demonstrated whitish blue intracellular granules under fluorescence microscope. The cells containing these granules were identified as histamine containing cells on microspectrofluorometry, because of accordance in excitation and emission spectra with authentic histamine. Histamine-containing cells were considered to be identical to the mast cells, because of metachromatic property on toluidine blue staining and of close structural similarities under electron microscope.

Histamine and peptic ulcer: a prospective study of mucosal histamine concentration in duodenal ulcer patients and in control subjects suffering from various gastrointestinal diseases

In a prospective study the histamine content of the mucosa of the body of the stomach was measured in 100 patients consisting of control subjects, patients with duodenal ulcer and patients suffering from various gastrointestinal diseases. The histamine content was found to be 43 mug/g in male control subjects (median) while in duodenal ulcer patients levels attained were significantly lower by about 30 per cent. In all the other groups of patients histamine concentrations in gastric mucosa were found to be "normal". Since in most species it is extremely diffcult to alter the mucosal histamine concentration by any form of treatment, the diminished histamine content of the gastric mucosa in patients with duodenal ulcer seems remarkable. Among several possible explanations offered for this finding we think the most likely is that histamine release is increased in duodenal ulcer disease.

Cytochemical and immunofluorescence investigations of insulin-like producing cells in the intestine of Mytilus edulis L. (Bivalvia)

Insulin-like immunoreactivity can be localized to cells of the intestine in the area of the hepatopancreas of Mytilus edulis L. No cross-reactivity can be obtained with anti-glucagon, anti-gastrin, anti-pentagastrin or anti-caerulin. The cells containing the substance immunoreactive to mammalian anti-insulin, can be restrained with paraldehyde-fuchsin.