Vasoactive intestinal peptide (VIP) cells in the pancreas and gastro-intestinal mucosa

Summary Using antibodies against pure porcine VIP in immunoperoxidase and immunofluorescence tests, VIP-immunoreactive cells have been detected in the pancreas—especially in the islets—and gastrointestinal mucosa of the dog, guinea-pig and man. VIP immunoreactive cells were widely distributed in these tissues, never being numerous at any site. Some parallelism has been noted between such cells and ultrastructurally identified D₁ cells of the pancreas and gastrointestinal mucosa. The presence of VIP cells in normal pancreas may help explain the occurrence of pancreatic endocrine tumors producing VIP.     

Immunohistochemical localization of some endocrine cells in the gastroenteropancreatic system of Erinaceus europaeus

The distribution of chromogranin A and neuron specific enolase (NSE) in the neuroendocrine gut system and the morphology and distribution of cells containing gastrin, somatostatin, neurotensin and VIP in the gastroenteropacreatic (GEP) apparatus of Erinaceus europaeus were investigated by immunohistochemical methods. Chromogranin A and somatostatin immunoreactive cells were present throughout the gastrointestinal mucosa, with the exception of the oesophagus and in the pancreas. Gastrin cells were peculiar of the pyloric glands and duodenal mucosa and neurotensin cells of the small intestine. No VIP immunoreactive endocrine cells were noticed in the GEP system. VIP and NSE immunoreactivities were detected both in nerve cell bodies and terminals of the wall of the GEP apparatus. NSE immunoreactivity was found in the endocrine cells of the fundic and pyloric mucosa.     

On the immunocytochemical localization of the vasoactive intestinal polypeptide.

The distribution of vasoactive intestinal polypeptide (VIP) immunoreactive nerves and endocrine cells in the gastrointestinal tract and pancreas of a number of mammalian and submammalian species has been examined in order to throw light on the exact localization of this peptide. Seven out of 8 VIP antisera demonstrated numerous nerve fibers in the gut, whereas one antiserum (TR2) revealed only scattered, few nerve fibers. The distribution of endocrine cells demonstrated by the different VIP antisera varied considerably. Thus, some antisera demonstrated only endocrine cells in the feline antrum, others only colonic endocrine cells and still others only endocrine cells of the upper gut and pancreas. The variability in staining pattern of endocrine cells as well as recent radioimmunological data makes it opportune to suggest that true VIP is a neuronal peptide and that endocrine cells store peptides resembling, but not being identical with, VIP (VIPoids).     

Distribution of retinol-binding protein in the human digestive tract.

By employing polyclonal antibodies for retinol-binding protein (RBP), its distribution in the human pancreas and digestive tract mucosa was compared with those of transthyretin (TTR) and various peptide hormones. The materials used included surgically removed pancreas, esophagus, stomach, small and large intestines. Paraffin sections were stained by the indirect immunoenzyme method. The results indicate that RBP-containing cells are found in the pancreas and the gastrointestinal mucosa, but most frequently in the gastric antrum and duodenum. In the pancreas, RBP-containing cells are found in the islets and among acinar and ductal epithelial cells, and consistently stain for chromogranin A. RBP-containing cells in the gastrointestinal mucosa showed typical features of endocrine cells and also stained for chromogranin A. The distribution of TTR in these tissue sites resembled that of RBP, but the immunoreactive intensities of both peptides altered independently. Comparison of the distribution of RBP, TTR, and various gastrointestinal peptide hormones revealed that the distribution of RBP coincided with none of the other peptides, although some of the RBP-containing cells stained for most of the peptides examined and vice versa. These results suggest that RBP may be a consistent component of gastrointestinal endocrine cells.     

Immunocytochemical investigation of the gastro-entero-pancreatic (GEP) neurohormonal peptides in the pancreas and gastrointestinal tract of the dogfish Squalus acanthias

The pancreas and gastrointestinal tract (GIT) of adults and of an embryonic stage of 11 cm long (about half the length of newborn fish) of the spiny dogfish, Squalus acanthias, were investigated immunocytochemically for the occurrence of the gastro-entero-pancreatic (GEP) neurohormonal peptides. In the pancreas of adult forms 5 endocrine cell types were seen, namely insulin-, somatostatin-, glucagon-, pancreatic polypeptide (PP)- and gastric inhibitory peptide (GIP)-immunoreactive cells. These cell types form scattered islets and were seen sometimes to surround small ducts. GIP-immunoreactivity cells did not occur in glucagon-containing cells. In the mucosa of GIT of adults 18 endocrine cell types were observed, viz. insulin-, somatostatin-, glucagon-, glicentin, PP-, polypeptide YY (PYY)-, vasoactive intestinal polypeptide (VIP)-, GIP-, gastrin C-terminus, CCK-, neurotensin N-terminus-, bombesin/gastrin releasing peptide (GRP)-, substance P-, enkephalin-, alpha-endorphin, beta-endorphin-, serotonin- and calcitonin immunoreactive cells. These cells occurred mostly in the intestine. All these cell types were of the open type, except glucagon- and glicentin-immunoreactive cells in the stomach, which seemed to be of the closed type. In the muscle layers and the submucosa, VIP and substance P- immunoreactive nerves and neurons were observed. In the pancreas of the dogfish embryo only 3 endocrine cell types could be demonstrated, namely insulin-, somatostatin- and glucagon-immunoreactive cells. In the mucosa of the GIT of the embryos studied 12 endocrine cell types were detected, viz. insulin-, somatostatin-, glucagon-, PP-, PYY-, VIP, GIP, gastrin C-terminus-, CCK-, neurotensin N-terminus-, enkephalin- and serotonin immunoreactive cells. The number of these cells, except that of PYY-immunoreactive cells, was lower than that of adults and in some cases their distribution did not correspond with that of adults.     

Complement-mediated binding of immunoglobulins to some endocrine cells of the pancreas and gut.

Unspecific binding of immunoglobulins to gastrin, somatostain and glucagon cells of the gastrointestinal mucosa or pancreas has been found to occur through a nonantigen-antibody mechanism mediated by the C14 fraction of complement. The phenomenon represents an important drawback in hormone immunohistochemistry, which can be overcome by using complement deprived, highly dilute anti-hormone sera.     

Immunocytochemical localization of vasoactive intestinal polypeptide in the digestive tracts of a holostean and a teleostean fish

1. The localization of vasoactive intestinal polypeptide (VIP) in the gastrointestinal tracts of a holostean fish, the bowfin (Amia calva) and a teleostean fish, the bluegill (Lepomis macrochirus) was determined using immunocytochemistry.2. In the bowfin, VIP immunoreactivity was observed in both gut nerves and gastrointestinal endocrine cells. In the bluegill, only gut nerves exhibited VIP-like immunoreactivity.3. The presence of VIP endocrine cells in the gastric mucosa of bowfin appears to be unique among vertebrates. VIP-containing endocrine cells of the open type were seen in cardiac, oxyntic, and antral gastric mucosa. There appeared to be morphological differences in VIP endocrine cell shapes in anterior versus posterior stomach regions. No VIP endocrine cells were observed in bowfin intestine.4. We conclude that VIP may have an endocrine/paracrine regulatory role in the bowfin stomach and may be strictly a neurotransmitter/neuromodulator in the bowfin gut. There are many species differences in the distribution of VIP-like peptides between neurons and endocrine cells in the guts of lower vertebrates, complicating analysis of the neural versus endocrine evolutionary origin of gut VIP.     

Autoradiographic distribution of vasoactive intestinal polypeptide receptors in rabbit and rat small intestine

Vasoactive intestinal peptide (VIP) is found in the enteric nervous system of all layers of the small intestine. In the gastrointestinal tract, VIP receptors coupled to adenylate cyclase are present on epithelial, smooth muscle and possibly mononuclear cells. This study analyzes the distribution of VIP binding using in vitro autoradiographic techniques. VIP binding was present in high density in the mucosal layer of rabbit duodenum, jejunum and ileum. Low VIP binding was noted over the smooth muscle layers or the lymphoid follicles. Similar results were obtained in rat small intestine. The density of VIP binding was greatest in duodenal mucosa but was present in lower density in jejunal and ileal mucosa. Again, low VIP binding was noted in the smooth muscle layers or lymphoid follicles. Thus, autoradiographic maps of small intestine indicate that VIP receptors are found primarily in the small intestinal mucosa.     

Immunocytochemical investigation of the gastro-enteropancreatic (GEP) neurohormonal peptides in the pancreas and gastrointestinal tract of the dogfishSqualus acanthias

Summary The pancreas and gastrointestinal tract (GIT) of adults and of an embryonic stage of 11 cm long (about half the length of newborn fish) of the spiny dogfish,Squalus acanthias, were investigated immunocytochemically for the occurrence of the gastro-entero-pancreatic (GEP) neurohormonal peptides. In the pancreas of adult forms 5 endocrine cell types were seen, namely insulin-, somatostatin-, glucagon-, pancreatic polypeptide (PP)- and gastric inhibitory peptide (GIP)-immunoreactive cells. These cell types form scatterd islets and were seen sometimes to surround small ducts. GIP-immunoreactivity cells did not occur in glucagon-containing cells. In the mucosa of GIT of adults 18 endocrine cell types were observed, viz. insulin-, somatostatin-, glucagon-, glicentin-, PP-, polypeptide YY (PYY)-, vasoactive intestinal polypeptide (VIP)-, GIP-, gastrin C-terminus, CCK-, neurotensin N-terminus-, bombesin/gastrin releasing peptide (GRP)-, substance P-, enkephalin-, -endorphin, -endorphin-, serotonin- and calcitonin immunoreactive cells. These cells occurred mostly in the intestine. All these cell types were of the open type, except glucagon- and glicentin-immunoreactive cells in the stomach, which seemed to be of the closed type. In the muscle layers and the submucosa, VIP and substance P-immunoreactive nerves and neurons were observed. In the pancreas of the dogfish embryo only 3 endocrine cell types could be demonstrated, namely insulin-, somatostatin- and glucagon-immunoreactive cells. In the mucosa of the GIT of the embryos studied 12 endocrine cell types were detected, viz. insulin-, somatostatin-, glucagon-, PP-, PYY-, VIP, GIP, gastrin C-terminus-, CCK-, neurotensin N-terminus-, enkephalin- and serotonin immunoreactive cells. The number of these cells, except that of PYY-immunoreactive cells, was lower than that of adults and in some cases their distribution did not correspond with that of adults.     

Vasoactive intestinal peptide (VIP) receptors in the canine gastrointestinal tract

Vasoactive intestinal peptide (VIP) is a putative neurotransmitter in both the brain and peripheral tissues. To define possible target tissues of VIP we have used quantitative receptor autoradiography to localize and quantify the distribution of ¹²⁵I-VIP receptor binding sites in the canine gastrointestinal tract. While the distribution of VIP binding sites was different for each segment examined, specific VIP binding sites were localized to the mucosa, the muscularis mucosa, the smooth muscle of submucosal arterioles, lymph nodules, and the circular and longitudinal smooth muscle of the muscularis externa. These results identify putative target tissues of VIP action in the canine gastrointestinal tract. In correlation with physiological data, VIP sites appear to be involved in the regulation of a variety of gastrointestinal functions including epithelial ion transport, gastric secretion, hemodynamic regulation, immune response, esophageal, gastric and intestinal motility.     

The distribution and cellular origin of vasoactive intestinal polypeptide in the avian gastrointestinal tract and pancreas

Summary The distribution and origins of vasoactive intestinal peptide (VIP) in the gut and pancreas of the turkey were studied by radioimmunoassay of tissue extracts and by immunocytochemistry. Several antisera were used that vary in their specificity for different regions of porcine or chicken VIP. Radioimmunoassays using NH₂-terminal specific antisera that react almost equally with porcine and chicken VIP's revealed significant amounts of immunoreactive VIP in extracts of pancreas, brain and all regions of the gastrointestinal tract from crop to colon. Highest concentrations (300pmol/g) were found in the colon muscle, and concentrations were generally low (< 20 pmol/g) in the mucosal layers of the small intestine. After ion exchange chromatography of extracts on CM-Sephadex three immunoreactive forms of VIP were separated corresponding to the three molecular forms previously found in mammalian gut extracts. In immunocytochemical studies nerve fibres were found throughout the gut, and in the pancreas. Immunoreactive nerve cell bodies were also identified in the submucous plexus throughout the gut, but were particularly prominent in the oesophagus and pancreas. It has previously been shown that VIP is a strong stimulant of the flow of pancreatic juice in birds whereas the structurally related hormone secretin, which is known to control the flow of pancreatic juice in mammals, is a weak stimulant. It is proposed that in birds VIP might regulate the pancreas, and other aspects of gut function, as a neurotransmitter or neurohormone.     

Regulatory peptide and serotonin content and brush-border enzyme activity in the rat gastrointestinal tract following neonatal treatment with capsaicin; lack of effect on epithelial markers.

The possible trophic influence of the capsaicin-sensitive extrinsic innervation of the gastrointestinal mucosa was investigated. Rats were treated neonatally with capsaicin. The gastrointestinal content of serotonin and glucagon-like immunoreactivity were used as a measure of the effect on the endocrine gut mucosa and gastrointestinal aminopeptidase and alkaline phosphatase activities were used as a measure of the effect on the gut brush-border. The gastrointestinal content of the neuropeptides substance P, VIP and CGRP were used to monitor effects on the innervation of the gut. The depletion of substance P-immunoreactivity(-IR) and calcitonin gene-related peptide(CGRP)-IR in extracts of urinary bladder and lung from the capsaicin-treated rats is evidence of the efficacy of capsaicin treatment in affecting a loss of C-fibre sensory nerves. The significant depletion of CGRP-IR measured in the stomach and duodenum of capsaicin-treated rats indicated the loss of the C-fibre sensory innervation to the gastrointestinal tract. The gastrointestinal content of VIP and substance P, which are predominantly within intrinsic gut neurones, were unaffected by capsaicin treatment. In all regions of the gastrointestinal tract of capsaicin-treated rats, the serotonin and glucagon-IR levels were not significantly different from those in controls. Similarly the levels of activity of the brush-border enzymes were not significantly effected by capsaicin treatment. This suggest the absence of any major trophic influence of capsaicin-sensitive sensory nerves on the gut endocrine mucosa and the brush border.     

Innervation of the pancreas by vasoactive intestinal polypeptide (VIP) immunoreactive nerves

The vasoactive intestinal polypeptide (VIP) has been shown to exert effects on endocrine and exocrine pancreatic secretion. Immunocytochemistry reveals that VIP immunoreactive nerves occur in the porcine, canine, feline and avian pancreas. In the pancreas of pig and cat VIP nerves are abundant around non-immunoreactive nerve cell bodies of the intrapancreatic ganglia but scarce in the islets and in the exocrine parenchyma. In the dog pancreas, however, the intrapancreatic ganglia contain strongly immunoreactive VIP nerve cell bodies which give off axons that seem to heavily innervate vessels as well as endocrine and exocrine cells. We suggest that in the pig and cat the pancreatic VIP nerves mainly affect the activity of a second type of intrapancreatic neuron, whose transmitter is unknown, whereas in the dog pancreas VIP nerves directly contact their putative effector structures.     

The effects of antagonists of receptors for gastrin, cholecystokinin and bombesin on growth of gastroduodenal mucosa and pancreas.

The effects of gastrin, cholecystokinin (CCK) and bombesin on the DNA synthesis, as a biochemical indicator of trophic action in the gastroduodenal mucosa and the pancreas have been examined in rats fasted for 48 h and in rats refed for 16 h with or without administration of specific receptor antagonists for bombesin, gastrin and CCK. Bombesin and gastrin administered three times daily for 48 h in fasted rats significantly increased the rate of DNA synthesis as measured by the incorporation of [3H] thymidine into DNA in each tissue tested. CCK significantly increased DNA synthesis in the duodenal mucosa and pancreatic tissue, but not in the gastric mucosa. The stimulation of DNA synthesis induced by bombesin in the gastroduodenal mucosa and pancreas was abolished by bombesin/GRP receptor antagonist, RC-3095. RC-3095 did not affect DNA synthesis stimulated by gastrin and CCK in these tissues. L-365,260, a receptor antagonist for gastrin suppressed the DNA synthesis induced by gastrin but not by CCK or bombesin in the gastrointestinal mucosa and pancreas. L-364,718 a specific antagonist for CCK receptors was effective only against CCK stimulated duodenal mucosa and pancreatic growth. Refeeding of 48 h fasting rats strongly enhanced the DNA synthesis in all tissues tested, and this effect was significantly reduced in the gastroduodenal mucosa by blocking only gastrin receptors (with L-365,260) and that in the duodenal mucosa and the pancreas by antagonizing of CCK receptors (with L-364,718). Antagonism of bombesin receptors (with RC-3095) did not significantly affect the stimulation of DNA synthesis induced by refeeding in all tissues tested. This study indicates that the stimulation of DNA synthesis can be achieved by exogenous gastrin, CCK and bombesin acting through separate receptor but that only gastrin and CCK play the major role in the postprandial stimulation of the growth of gastroduodenal mucosa and pancreatic tissue.     

VIP and PHI in cat neurons: co-localization but variable tissue content possible due to differential processing

The concentrations of vasoactive intestinal polypeptide (VIP) and the peptide with NH2- terminal histidine and COOH-terminal isoleucine (PHI) in various peripheral tissues and some areas in the CNS of the cat were compared with their immunohistochemical localization. The VIP levels in the gastrointestinal tract were 3 to 6 times higher than PHI levels. Much (up to 10-fold) higher VIP than PHI levels were also observed in the genitourinary tract as well as in the lung and heart. In the neurohypophysis, however, the VIP/PHI ratio was close to 1. Gel-permeation chromatography revealed that VIP- and PHI-immunoreactivity (IR) in the intestine, pancreas and brain consisted of three larger molecular forms in addition to the 'standard' peptides. These larger forms which had overlapping elution positions may represent prepro-VIP/PHI forms. The immunohistochemical analysis revealed that VIP- and PHI-IR was present in the same ganglion cells in the intestine, pancreas, uterus and sympathetic ganglia. Furthermore, the terminal networks for these two peptides were very similar in the periphery. In the median eminence of the hypothalamus and in the posterior lobe of the pituitary, considerably more nerves were PHI- than VIP-IR. This observation was in parallel to a low VIP/PHI ratio. In conclusion, VIP and PHI seem to co-exist in most neuronal systems. Although the ratio of VIP and PHI on the precursor gene is 1:1, differences in posttranslational processing may create a considerably higher content of VIP than PHI in most terminal areas.     

Comparative study on the appearance of various bioactive peptides in foregut derivates during the ontogenesis.

Bioactive peptides have an important multifunctional role in the gastrointestinal tract. In the present study we have investigated the dynamism of the appearance of PACAP (pituitary adenylate cyclase activating polypeptide), VIP (vasoactive intestinal polypeptide), gastrin, and secretin immunoreactivities in human foregut derivates during the ontogenesis using an immunohistochemical approach. None of these peptides were observed in the foregut derivates of an 8-week-old embryo. VIP immunoreactive nerve fibers appeared by the 11th week in the smooth muscle layers of the stomach. No other peptide immunoreactivities were observed of this stage. In 18- and 20-week old fetuses PACAP, secretin, and gastrin immunoreactive cells appeared in the developing glands of the stomach. In the duodenum gastrin immunoreactivity was present in the Lieberkühn's glands and secretin immunoreactive cells were seen between the surface epithelial cells. In the pancreas secretin immunoreactivity was found in the Langerhans islets; however, PACAP immunreactivity was observed in the exocrine portion. The distribution of VIP fibers did not change during the fetal life and it was similar to the adult pattern. According to our results the appearance of PACAP, secretin, and gastrin in the developing glands suggests their role in the proliferation and differentiation of the epithelial derivates.     

The effect of antagonist of receptors for gastrin, cholecystokinin and bombesin on growth of gastroduodenal mucosa and pancreas.

The effects of gastrin, cholecystokinin (CCK) and bombesin on the DNA synthesis, as a biochemical indicator of trophic action in the gastroduodenal mucosa and the pancreas, have been examined in rats fasted for 48 h and in rats refed for 16 h with or without administration of specific receptor antagonists for bombesin, gastrin and CCK. Bombesin and gastrin administered three times daily for 48 h in fasted rats significantly increased the rate of DNA synthesis as measured by the incorporation of [3H] thymidine into DNA in each tissue tested. CCK significantly increased DNA synthesis in the duodenal mucosa and pancreatic tissue, but not in the gastric mucosa. The stimulation of DNA synthesis induced by bombesin in the gastroduodenal mucosa and pancreas was abolished by bombesin/GRP receptor antagonist, RC-3095. RC-3095 did not affect DNA synthesis stimulated by gastrin and CCK in these tissues. L-365,260, a receptor antagonist for gastrin suppressed the DNA synthesis induced by gastrin but not by CCK or bombesin in the gastrointestinal mucosa and pancreas. L-364,718, a specific antagonist for CCK receptors was effective only against CCK stimulated duodenal mucosa and pancreatic growth. Refeeding of 48 h fasting rats strongly enhanced the DNA synthesis in all tissues tested, and this effect was significantly reduced in the gastroduodenal mucosa by blocking only gastrin receptors (with L-365, 260) and that in the duodenal mucosa and the pancreas by antagonizing of CCK receptors (with L-364,718). Antagonism of bombesin receptors (with RC-3095) did not significantly affect the stimulation of DNA synthesis induced by refeeding in all tissues tested. This study indicates that the stimulation of DNA synthesis can be achieved by exogenous gastrin, CCK and bombesin acting through separate receptors, but that only gastrin and CCK play the major role in the postprandial stimulation of the growth of gastroduodenal mucosa and pancreatic tissue.     

Immunohistochemical study on the distribution of vasoactive intestinal polypeptide (VIP) containing nerve fibers in the chicken pancreas

The distribution of vasoactive intestinal polypeptide (VIP) containing nervous elements in the chicken pancreas was immunohistochemically investigated by light microscopy. Strongly VIP immunoreactive ganglia existed in the interlobular connective tissue. Ganglion containing both VIP immunoreactive and non-immunoreactive nerve cells was occasionally observed in the connective tissue. Almost all the ganglion cells also showed acetylcholinesterase (AChE) activity. No extrapancreatic nerve bundles containing VIP immunoreactive nerve fibres were detected. VIP immunoreactive nerve fibres formed plexuses in the subepithelial layer of secretory ducts and the muscle layer of small arteries. The distribution pattern of VIP immunoreactive nerve fibers was similar to that of AChE-positive nerve fibers on adjacent sections. The exocrine pancreas received a rich supply of varicose nerve fibers showing VIP immunoreactivity. B-islets also were richly innervated by VIP immunoreactive varicose nerve fibers, whereas A-islets, only poorly. These observations suggest that VIP containing nerves in the chicken pancreas have an intrinsic origin, are probably derived from VIP immunoreactive, intrapancreatic ganglion cells and innervate secretory ducts, arteries, acinar cells and B-islets, and that VIP must coexist with acetylcholine in the nervous elements.     

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.