A pancreatic polypeptide (PP)-like immunoreactant is present in the glicentin-containing cell of the cat intestine

Summary BPP-like immunoreactivity was identified in the intestinal mucosa of the cat. In light microscopy BPP immunoreactive cells were found identical to glicentin-containing cells or L-cells. By immunoelectronmicroscopy, BPP-like material was localized within the glicentin-containing secretory granules.This work was supported by grant nr. 3.120.77 from the Swiss National Science Foundation     

An Ultrastructural and Immunocytochemical Study of Gastrodermal Cell Types in Microstomum lineare (Turbellaria,Macrostomida)

The gastrodermal cell types of Microstomum lineare (Turbellaria, Macrostomida) were studied by electron microscopy. Their immunoreactivity (IR) to bovine pancreatic peptide (BPP), FMRF-amide and vasotocin, somatostatin, neurotensin, ACTH, CCK, bombesin, secretin, gastrin/CCK and insulin antisera was tested by light microscopic immunocytochemical methods. In addition to granular club cells and phagocytic cells, neurons and neoblasts occur in the gastroderm of this turbellarian species. This is the first observation of neurons in the gastroderm of a flatworm. Dense-core vesicles (70–100 nm diameter), electron lucent cytoplasm and numerous Golgi complexes characterize the neurons. Unpolarized two-way synapses, neuromuscular junctions and polarized chemical synapses can be observed in the gastroderm. Neoblasts with large nuclei and scanty cytoplasm and differentiating cells containing clusters of basal bodies occur next to the basal lamina of the gastroderm. BPP-like, FMRF-amide-like and vasotocin-like immunoreactivity is demonstrated in the gastroderm. Both BPP and FMRF-amide IR is restricted to the basal cytoplasm of the granular club cells, while a different location for IR to vasotocin antiserum is observed. The status of the neuronal cell in the gastroderm of M. lineare is discussed in relation to endocrine (paracrine) cells and neurons in the gastroderm of invertebrates.     

Ontogeny of immunoreactive glicentin in the human gastrointestinal tract and endocrine pancreas

The gestational time of appearance and distribution of immunoreactive glicentin was compared to that of immunoreactive glucagon in the gastrointestinal tract and endocrine pancreas of human fetuses, aged between 5 and 24 weeks, by an indirect immunoperoxidase method. With the glicentin antiserum No. R 64, the first immunoreactive cells were detected at the 10th week of gestation in the oxyntic mucosa and proximal small intestine, at the 8th week in the ileum and at the 12th week in the colon. In the endocrine pancreas, the first immunoreactive cells were observed as early as 8 weeks within the walls of the primitive pancreatic ductules. At a more advanced stage of development (12 weeks), they were found interspersed among the islet cell clusters and still later (16 weeks) inside the recognizable islets of Langerhans. With the glucagon antiserum No. GB 5667, no immunoreactive cells were demonstrated in the gastrointestinal tract whatever the age of the fetuses. In the endocrine pancreas, the first immunoreactive cells were observed at the 8th week of gestation in the pancreatic parenchyma. The distribution of glucagon-containing cells in the pancreas was similar to that of glicentin immunoreactivity throughout ontogenesis. In the pancreatic islets of one 18-week-old human fetus, the study of consecutive semithin sections treated by both antisera showed that the same cells were labelled. The significance of these findings concerning the role of glicentin as a glucagon precursor is discussed.     

Differential profile of CRF receptor distribution in the rat stomach and duodenum assessed by newly developed CRF receptor antibodies

Peripheral corticotropin-releasing factor (CRF) receptor ligands inhibit gastric acid secretion and emptying while stimulating gastric mucosal blood flow in rats. Endogenous CRF ligands are expressed in the upper gastrointestinal (GI) tissues pointing to local expression of CRF receptors. We mapped the distribution of CRF receptor type 1 (CRF1) and 2 (CRF2) in the rat upper GI. Polyclonal antisera directed against the C-terminus of the CRF receptor protein were generated in rabbits and characterized by western blotting and immunofluorescence using CRF1- and CRF2-transfected cell lines and in primary cultured neurons from rat brain cortex. A selective anti-CRF1 antiserum (4467a-CRF1) was identified and used in parallel with another antiserum recognizing both CRF1 and CRF2 (4392a-CRF1&2) to immunostain gastric tissue sections. Antiserum 4467a-CRF1 demonstrated specific immunostaining in a narrow zone in the upper oxyntic gland within the stomach corpus. Conversely, 4392a-CRF1&2 labeled cells throughout the oxyntic gland and submucosal blood vessels. Pre-absorption with the specific antigen peptide blocked immunostaining in all experiments. Doublestaining showed co-localization of 4392a-CRF1&2 but not 4467a-CRF1 immunoreactivity with H/K-ATPase and somatostatin immunostaining in parietal and endocrine cells of the oxyntic gland. No specific staining was observed in the antrum with either antisera, whereas only antiserum 4392a-CRF1&2 showed modest immunoreactivity in the duodenal mucosa. Finally, co-localization of CRF2 and urocortin immunoreactivity was found in the gastric glands. These results indicate that both CRF receptor subtypes are expressed in the rat upper GI tissues with a distinct pattern and regional differences suggesting differential function.     

Ontogeny of histamine-immunoreactive cells in rat stomach

Summary An antiserum against hemocyanin-conjugated histamine was used to study the cellular stores of histamine in the stomach, especially the oxyntic mucosa, of fetal and early postnatal rats. Tissues were fixed in 4% 1-ethyl-3(3-dimethyl-aminopropyl) carbodiimide (EDC-DI) and standard immunofluorescence technique was used. Histamine was first detected on the 16th embryonic (E16) day when a few histamine-immunoreactive (HA-ir) cells and nerve fibers were observed in the muscular layer of the stomach wall. On day E18, HA-ir cells were visualized for the first time in the oxyntic mucosa of the stomach, and from that day on the number of such cells increased slowly initially and after day E20 more rapidly. At birth many of the HA-ir cells in the oxyntic mucosa possessed processes giving them a paracrine-like appearance typical of enterochromaffin-like cells (ECL cells). Only a very small number of the HA-ir cells represented metachromatically stained mast cells and were located in the submucosa. After birth, the number of HA-ir ECL cells increased steadily, until day 21 when the distribution and number was very similar to that of the adult. The results suggest that histamine-containing neurons and ECL cells appear in the stomach wall before birth, and that there are histamine-containing ECL cells in the mucosa and mast cells in the submucosa of the stomach wall at birth.     

Histamine and histidine decarboxylase are hallmark features of ECL cells but not G cells in rat stomach

The oxyntic mucosa of the rat stomach is rich in ECL cells which produce and secrete histamine in response to gastrin. Histamine and the histamine-forming enzyme histidine decarboxylase (HDC) have been claimed to occur also in the gastrin-secreting G cells in the antrum. In the present study, we used a panel of five HDC antisera and one histamine antiserum to investigate whether histamine and HDC are exclusive to the ECL cells. By immunocytochemistry, we could show that the ECL cells were stained with the histamine antiserum and all five HDC antisera. The G cells, however, were not stained with the histamine antiserum, but with three of the five HDC antisera. Thus, histamine and HDC coexist in the ECL cells (oxyntic mucosa) but not in G cells (antral mucosa). Western blot analysis revealed a typical pattern of HDC-immunoreactive bands (74, 63 and 54 kDa) in oxyntic mucosa extracts with all five antisera. In antral extracts, immunoreactive bands were detected with three of the five HDC antisera (same as above); the pattern of immunoreactivity differed from that in oxyntic mucosa. Food intake of fasted rats or treatment with the proton pump inhibitor omeprazole raised the HDC activity and the HDC protein content of the oxyntic mucosa but not of the antral mucosa; the HDC activity in the antrum was barely detectable. We suggest that the HDC-like immunoreactivity in the antrum represents a cross-reaction with non-HDC proteins and conclude that histamine and HDC are hallmark features of ECL cells but not of G cells.     

Effect of reserpine on the generation of the chromogranin A-derived neuropeptide WE-14 in rat oxyntic mucosa

WE-14, a post-translational product of the neuroendocrine protein chromogranin A (CgA), is generated in distinct subpopulations of endocrine cells. The objective of this study was to investigate the generation of WE-14 in the endocrine cell types of the oxyntic mucosa of the stomach, after treatment with reserpine, an irreversible inhibitor of vesicular monoamine uptake 2 (VMAT2). Reserpine (10 mg/kg) was administered subcutaneously and tissue analysed 1, 3, 5 and 18 h following treatment. The oxyntic mucosa was analysed immunohistochemically employing a site-specific WE-14 antiserum, a region-specific CgA antiserum and an antiserum against histidine decarboxylase (HDC), a marker of the histamine-producing ECL cells in the oxyntic mucosa. The number of oxyntic endocrine cells exhibiting WE-14 immunostaining increased more than 100-fold 18 h after reserpine administration relative to vehicle treated controls. Double immunostaining with HDC revealed that most, but not all, of the WE-14 positive cells were ECL cells. These results suggest that reserpine has the ability to influence the post-translational processing of CgA to generate WE-14 in rat stomach ECL cells, presumably as a consequence of reduced VMAT2-driven accumulation of histamine.     

An FMRFamide antiserum differentiates between populations of antigens in the ventral nervous system of the locust,Schistocerca gregaria

Summary The distribution of FMRFamide immunoreactive neurones in the ventral nerve cord of the locust, Schistocerca gregaria, is described. These neurones are found only in the suboesophagael and thoracic ganglia, although immunoreactive processes are found in the neuropils of the abdominal ganglia. Many of these neurones also react with an antiserum raised against bovine pancreatic polypeptide (BPP), but this antiserum also reveals another population of cells in the abdominal ganglia. The staining obtained with the BPP antiserum is blocked by preabsorption of the antiserum with FMRFamide; the converse is not true: FMRFamide-like immunoreactivity is not suppressed by preincubation with BPP. These results suggest that there are at least two endogenous peptide antigens in the locust nerve cord: one is found in cells of the suboesophageal and thoracic ganglia, and the other is found in cells of the abdominal ganglia.     

A-like cells in the rat stomach contain ghrelin and do not operate under gastrin control

Ghrelin is a 28 a.a. gastric peptide, recently identified as a natural ligand of the growth hormone secretagogue receptor (orphan receptor distinct from the receptor for growth hormone releasing hormone). In the present study, radioimmunoassay demonstrated ghrelin-like material in the rat oxyntic mucosa with moderate amounts also in antrum and duodenum. Small amounts were found in the distal intestines and pancreas. Northern blot analysis revealed abundant ghrelin mRNA in the oxyntic mucosa. Immunocytochemistry demonstrated ghrelin-immunoreactivity in endocrine-like cells in the oxyntic mucosa. Such cells occurred in low numbers also in the antrum and duodenum. The rat oxyntic mucosa is rich in endocrine (chromogranin A/pancreastatin-immunoreactive) cells, such as the histamine-rich ECL cells (65-75% of the endocrine cells), the A-like cells (20-25%) and the D cells (somatostatin cells) (10%). The ghrelin-immunoreactive (IR) cells contained pancreastatin but differed from ECL cells and D cells by being devoid of histamine-forming enzyme (ECL cell constituent) and somatostatin (D cell constituent). Hence, ghrelin seems to occur in the A-like cells. The ghrelin-IR cells in the antrum were distinct from the gastrin cells, the serotonin-containing enterochromaffin cells and the D cells. Conceivably, ghrelin cells in the antrum and distally in the intestines also belong to the A-like cell population. The concentration of ghrelin in the circulation was lowered by about 80% following the surgical removal of the acid-producing part of the stomach in line with the view that the oxyntic mucosa is the major source of ghrelin. The serum ghrelin concentration was higher in fasted rats than in fed rats; it was reduced upon re-feeding and seemed unaffected by 1-week treatment with the proton pump inhibitor omeprazole, resulting in elevated serum gastrin concentration. Infusion of gastrin-17 for 2 days failed to raise the serum ghrelin concentration. Omeprazole treatment for 10 weeks raised the level of HDC mRNA but not that of ghrelin mRNA or somatostatin mRNA in the oxyntic mucosa. Hence, unlike the ECL cells, ghrelin-containing A-like cells do not seem to operate under gastrin control.     

Anglerfish islets contain NPY immunoreactive nerves and produce the NPY analog aPY

It has recently been demonstrated that aPY, a peptide which has significant homology with neuropeptide Y (NPY) is present in extracts of anglerfish islets. The purpose of this study was to determine whether cells or nerves which contain NPY-like immunoreactivity could be identified in anglerfish islet tissue and whether aPY is synthesized by this tissue. Antisera against bovine pancreatic polypeptide (BPP), NPY and the 200 kd neurofilament polypeptide were used for immunohistochemical analysis of islets. Identical cells were stained by both the NPY and BPP antisera. The NPY and 200 kd neurofilament antisera also labeled nerve fibers in the tissue which were not stained with the BPP antiserum. The nature of the NPY-like peptide synthesized in islet cells was determined by subjecting differentially radioactively labeled Mr 2,500-8,000 peptides from islet extracts to reverse phase HPLC. Labeled aPY was unequivocally identified in the extracts and was labeled appropriately (as predicted from its sequence) with 13 different radioactive amino acids. These results demonstrate that one form of NPY-like peptide synthesized in anglerfish islets is aPY. The form of NPY-like peptide which was immunolocalized in nerves remains to be determined.     

FMRF-amide immunoreactivity in a moth larva (Heliothis zea): The cerebral nervous system

The cerebral nervous system of the larval corn earworm, Heliothis zea, was examined using light microscopy and immunocytochemistry. Immunoreactivity for the molluscan cardioactive peptide FMRF-amide (FMRFa) is widely distributed. Staining is localized in perikarya and axons of the brain, subesophageal ganglion and first thoracic ganglion. Immunoreactive axons are also found in the frontal ganglion and the corpora cardiaca. Crossreactivity studies for FMRFa and bovine pancreatic polypeptide (BPP) demonstrate that (a) the immunoreactive material is more FMRFa-like than BPP-like and (b) the antigenic material is heterogeneous. For animals on different feeding regimens, immunocytochemical surveys and radioimmunoassay suggest the observed variation in immunoreactivity among individuals is unrelated to feeding state.     

Enzymatic cleavage prior to antibody incubation as a method for neuropeptide immunocytochemistry

Summary Five anti-gastrin releasing peptide (GRP) sera have been characterized against GRP, bombesin and related polypeptides spotted on cellulose acetate discs. Antibodies reacting with the C-terminal G-14 sequence of bombesin and the 19–27 sequence of GRP, were detected in all sera. Antibodies directed exclsively against the bombesin unrelated 1–17 sequence of GRP were found only in one serum (R-6902). With parallel immunohistochemical tests only the C-terminal immunoreactivity was detected in endocrine-paracrine cells of the chicken proventriculus, while both immunoreactivities were present in nerve fibres and a few nerve cell bodies of the mammalian gut. The distribution of GRP- and bombesin-like immunoreactive nerves in the gastric mucosa of both pyloric and oxyntic type the submucosal and myenteric plexus along the whole gastrointestinal wall and at sphincter regions is detailed.     

Ontogeny and distribution of certain endocrine cells in the human fetal large intestine

Summary In 9 fetuses, 9 to 24 weeks-old, the occurrence and relative distribution of argentaffin cells, as well as of cells immunoreactive to somatostatin (SRIF), glucagon-like polypeptide (GLI), pancreatic polypeptide (PP) and substance P (SP) were studied in five segments of the colon (appendix, cecum, ascending colon, descending colon, and rectosigmoid). For each colonic segment, data concerned with the occurrence of endocrine cells were expressed either as mean absolute numbers of specific cells per entire mucosal section, or as cell densities per mm³ of mucosa after calculation of the mucosal volume of the sections. Argentaffin, GLI, SRIF and PP immunoreactive cells are all present in relatively large numbers, scattered along the entire length of the colonic mucosa as early as the 9th–10th week of gestation, whereas substance P-containing cells occur sporadically and first appear during the 14th–17th week. Until the 20th week, with progressing embryonic development, an increase was determined in absolute numbers per section of all types of endocrine cells in all segments of the colon. This observation is clearly related to the general growth of the colonic mucosa, since cell densities per mm³ of mucosa do not greatly change or even decrease during gestation. However, it is possible that densities of argentaffin, GLI and BPP cells increase in the appendix around the 14th–17th week of gestation. Between the 20th and 24th week, absolute numbers of cells per section remain stable or slightly increase, while cell densities tend rather to decrease in all segments. These data demonstrate that some endocrine cells are present very early in the human fetal colon, but their functional significance remains to be elucidated.This work was supported by the Institut National de la Santé et de la Recherche Médicale (INSERM)     

Role of hypergastrinemia in the antiatrophy effect of 2,3,7,8-tetrachlorodibenzo-p-dioxin on oxyntic gland mucosa of the rat stomach

Atrophy of the gastrointestinal mucosa that occurs in pair-fed control rats is not observed in 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)-treated rats (1). Our objective was to determine if the gastrointestinal trophic hormone, gastrin, is involved in the antiatrophy effect of TCDD on the gut mucosa. Adult male Sprague-Dawley rats treated with 100 micrograms/kg of TCDD were slightly hypergastrinemic 7 days after dosing and markedly hypergastrinemic 14 days after treatment whereas pair-fed control rats were normogastrinemic. After 14 days of feed restriction, atrophy of the oxyntic gland and ileum mucosa occurred in pair-fed control rats but only atrophy of the ileum mucosa developed in TCDD-treated animals. The oxyntic gland mucosa of TCDD-treated rats was protected from mucosa atrophy as well as from mucosa erosions. The protection against feed restriction-induced atrophy was demonstrated by measurements of oxyntic gland mucosal height and DNA and protein content. Since hypergastrinemia stimulates growth of oxyntic gland mucosa, but not ileum mucosa, the antiatrophy effect of TCDD on mucosa of the oxyntic gland might in part be due to hypergastrinemia. In support of this interpretation, TCDD treatment exerted an antiatrophy effect on the oxyntic gland mucosa only when TCDD-treated animals were hypergastrinemic. For example, hypergastrinemia does not develop within the first 48 hr after TCDD administration, and TCDD treatment affords no protection against fasting-induced atrophy of the oxyntic gland mucosa during this time. On the other hand, the ability of TCDD treatment to protect against feed restriction-induced erosions of the oxyntic gland mucosa might be mediated by hypergastrinemia since these events occur at a later time.(ABSTRACT TRUNCATED AT 250 WORDS)     

Exocrine pancreas under experimental conditions

Summary At least four types of endocrine-like cells have been detected histochemically in the mucosa of the human colon and rectum, i.e. argentaffin cells storing 5-hydroxytryptamine (5 HT) and non-argentaffin cells reacting with glucagon, somatostatin and bovine pancreatic peptide (BPP) antibodies. Ultrastructurally, four main types and three rare types of endocrine-like cells have been identified. Among the former cells were: (1) argentaffin EC₁ cells, known to store 5 HT and substance P, (2) poorly argyrophil L cells, corresponding to the glucagon-immunoreactive cells storing enteroglucagon or glucagon-like immunoreactivity (GL1), (3) inconstantly argyrophil F-like cells, possibly corresponding to BPP-immunoreactive cells, and (4) fairly argyrophil H cells of unknown function. Rare D cells, corresponding to somatostatin cells, N cells, corresponding to neurotensin cells, and P cells, of unknown function, have been also found.Supported in part by the Italian National Research Council (Grant N. 76.01558.04)     

Role of gastrin in the development of gastric mucosa,ECL cells and A-like cells in newborn and young rats

Histamine-producing ECL cells and ghrelin-producing A-like cells are endocrine/paracrine cell populations in the acid-producing part of the rat stomach. While the A-like cells operate independently of gastrin, the ECL cells respond to gastrin with mobilization of histamine and chromogranin A (CGA)-derived peptides, such as pancreastatin. Gastrin is often assumed to be the driving force behind the postnatal development of the gastric mucosa in general and the ECL cells in particular. We tested this assumption by examining the oxyntic mucosa (with ECL cells and A-like cells) in developing rats under the influence of YF476, a cholecystokinin-2 (CCK(2)) receptor antagonist. The drug was administered by weekly subcutaneous injections starting at birth. The body weight gain was not affected. Weaning occurred at days 15-22 in both YF476-treated and age-matched control rats. Circulating gastrin was low at birth and reached adult levels 2 weeks after birth. During and after weaning (but not before), YF476 greatly raised the serum gastrin concentration (because of abolished acid feedback inhibition of gastrin release). The weight of the stomach was unaffected by YF476 during the first 2-3 weeks after birth. From 4 to 5 weeks of age, the weight and thickness of the gastric mucosa were lower in YF476-treated rats than in controls. Pancreastatin-immunoreactive cells (i.e. all endocrine cells in the stomach) and ghrelin-immunoreactive cells (A-like cells) were few at birth and increased gradually in number until 6-8 weeks of age (control rats). At first, YF476 did not affect the development of the pancreastatin-immunoreactive cells, but a few weeks after weaning, the cells were fewer in the YF476 rats. The ECL-cell parameters (oxyntic mucosal histamine and pancreastatin concentrations, the histidine decarboxylase (HDC) activity, the HDC mRNA levels and serum pancreastatin concentration) increased slowly until weaning in both YF476-treated and control rats. From then on, there was a further increase in the ECL-cell parameters in control rats but not in YF476 rats. The postnatal development of the ghrelin cells (i.e. the A-like cells) and of the A-like cell parameters (the oxyntic mucosal ghrelin concentration and the serum ghrelin concentrations) was not affected by YF476 at any point.We conclude that gastrin affects neither the oxyntic mucosa nor the endocrine cells before weaning. After weaning, CCK(2) receptor blockade is associated with a somewhat impaired development of the oxyntic mucosa and the ECL cells. While gastrin stimulation is of crucial importance for the onset of acid secretion during weaning and for the activation of ECL-cell histamine formation and secretion, the mucosal and ECL-cell growth at this stage is only partly gastrin-dependent. In contrast, the development of the A-like cells is independent of gastrin at all stages.     

Gastrin-releasing peptide: neuronal distribution and spatial relation to endocrine cells in the human upper gut

By using immunocytochemical techniques, we have studied the distribution of gastrin releasing peptide (GRP)-containing neurons as well as the spatial relationship between these neurons and the endocrine cells in the human stomach and duodenum. Moderate numbers of immunoreactive fibers were distributed in the smooth muscle and submucosa of the stomach; they were more rare in the duodenal wall. Numerous GRP-containing nerve fibers were found in the oxyntic mucosa, the antral mucosa harboured only few GRP immunoreactive nerve fibers. The mucosa of the proximal duodenum was found to be virtually devoid of such fibers. Only occasionally did we observe signs of a direct contact between GRP-containing nerve fibers and gastrin and somatostatin cells in the antral mucosa. In the oxyntic mucosa GRP-containing nerve fibers sometimes seemed to contact endocrine cells, including somatostatin cells as well as individual parietal cells. In conclusion, although GRP-containing nerve fibers were quite numerous in the wall of the human upper gastro-intestinal (GI)-tract, we observed a lack of intimate spatial relationship between these fibers and endocrine cells in the antral mucosa, suggesting additive mechanisms to a direct innervation of gastrin cells and somatostatin cells by GRP nerve fibers explaining the physiological effects on hormonal release.     

Immunohistochemical studies on glucagon, glicentin and pancreatic polypeptide in human stomach: normal and pathological conditions

Summary Endocrine-like cells containing glucagon, glicentin or pancreatic polypeptide immunoreactivity in human foetal and adult stomach, with or without disease, were studied with the indirect immunoperoxidase method and mirror sectioning technique. In foetal and neonatal oxyntic mucosae, there were endocrine-like cells with glucagon and glicentin immunoreactivities and argyrophilia. Cells containing glicentin immunoreactivity alone were detected earlier than glucagon cells during foetal development, and were also distributed throughout foetal to neonatal life. Bovine pancreatic polypeptide immunoreactivity coexisted in a subpopulation of the glucagon-glicentin cells. These cells were absent from normal oxyntic mucosa in the postneonatal period and from normal antral mucosa throughout life. Hamartomatous polyp in adult oxyntic mucosa, hyperplastic oxyntic mucosa in Menetrier's disease and atrophic oxyntic mucosa in a remnant stomach with cancer showed scattered glucagon-glicentin cells, but few or no cells containing bovine pancreatic polypeptide. Intestinalized mucosa showed plentiful glicentin cells with occasional glucagon and/or bovine pancreatic polypeptide immunoreactivity. Some gastric cancer cells of both diffuse and adenoplastic types contained immunoreactive glicentin and, less frequently, glucagon. Bovine pancreatic polypeptide immunoreactivity was detected in a few adenoplastic cancer cells, but not in diffuse type cells. Three different anti-pancreatic polypeptide sera against bovine, porcine or human pancreatic polypeptide detected basically the same cells mentioned above, but pancreatic polypeptide cells lacking human pancreatic polypeptide immunoreactivity were also present in foetal oxyntic mucosa. Immunoabsorption tests revealed that the bovine pancreatic polypeptide immunoreactivity was remote from peptide YY and neuropeptide Y.     

Glicentin: A precursor of glucagon?

The relationships between glucagon and gut-glucagon like immunoreactants (gut-GLIs) have been investigated by immunofluorescence in canine gut mucosa. The R64 antiserum, raised against the purified gut-GLI-l glicentin, and which does not react with porcine glucagon, revealed immunofluorescent cells in the gastric and intestinal mucosa. Glicentin positive cells of the stomach oxyntic glands were also stained by N- and C- terminally directed antiglucagon sera, corresponding to the gastric A-cell. In the small and large intestine, glicentin immunoreactive cells reacted solely with the cross-reacting (N-terminal) glucagon antiserum, belonging to the L-cells. Based on chemical and immunochemical data, it has been suggested that glicentin could represent an intermediate in the glucagon biosynthesis. Therefore, the results of this immunofluorescence study, showing glicentin and glucagon immunodeterminants in the A-cell, strongly support such an hypothesis. In addition the presence of glicentin like material in the A- and L-cells suggests that these two cell types synthesize their secretory product via a common precursor.     

Gastrin and somatostatin in the rat antrum. The effect of removal of acid-secreting mucosa

Female rats were subjected to operations aimed at reducing the amount of oxyntic gland mucosa draining its acid secretion to the antrum. The rats were provided either with Heidenhain or Pavlov pouches reducing the oxyntic mucosa draining its secretion to the antrum by about 50% or subjected to various degrees (75, 90 and 100%) of fundectomy. Ten weeks following surgery, plasma levels of gastrin and somatostatin were assayed. At the same time, antral mucosal content of gastrin and somatostatin was determined as well as the mucosal density of these hormone-producing cells. There was a relationship between the amount of acid-secreting mucosa removed and the ensuring plasma concentration of gastrin. Thus, a stepwise increase in plasma gastrin was found with the highest levels obtained in rats subjected to 90 or 100% fundectomy. The somatostatin concentration in plasma was reduced only in rats subjected to fundectomy with the most sustained decrease in animals in which all oxyntic gland mucosa had been removed. There was also a relationship between the amount of acid-secreting mucosa removed and the gastrin content of the antral mucosa. An inverse relationship seemed to exist between antral gastrin and somatostatin concentrations. However, a significant decrease in somatostatin concentration of the antral mucosa was seen only in rats subjected to a fundectomy. The number of gastrin cells in the antral mucosa was increased in fundectomized rats only, with the largest density seen in rats deprived of all oxyntic mucosa. A corresponding decrease in the number of somatostatin cells was noticed. Our results would suggest an apparent functional relationship between antral gastrin and somatostatin cells, where the antral acid load (or pH) appears to be the major factor of physiological significance.