Gastrin-releasing Peptide Immunoreactivity Research Articles

Gastrin releasing peptide immunoreactivity is present in ovine amniotic fluid and fetal and maternal circulations. MRC Group in Fetal and Neonatal Health and Development

Gastrin releasing peptide immunoreactivity is present in ovine amniotic fluid and fetal and maternal circulations. MRC Group in Fetal and Neonatal Health and Development

Gastrin releasing peptide immunoreactivity is present in ovine amniotic fluid and fetal and maternal circulations. MRC Group in Fetal and Neonatal Health and Development.

Using antisera directed towards the C-terminal region of gastrin releasing peptide (GRP), significant quantities of GRP-like immunoreactivity (GRPLI) were detected in ovine amniotic fluid and in the fetal and maternal circulations. The highest GRPLI levels were found in amniotic fluid (2135 +/- 829 fmol/ml, n = 12; mean +/- SEM), followed by those in ovine fetal (604 +/- 267 fmol/ml, n = 13) and maternal plasma (229 +/- 89 fmol/ml, n = 13). On gel filtration chromatography, the predominant GRPLI form in each fluid eluted in an identical position consistent with the entity being of apparently larger molecular size than porcine GRP1-27. Certain fetal plasma samples contained a second GRPLI peak eluting at the void volume. Hence, during ovine pregnancy a GRPLI entity circulates in fetal and maternal plasma; the entity is of apparently larger molecular size than GRP1-27 but contains a structure immunologically indistinguishable from the bioactive c-terminal region of GRP1-27. Given the recognized bioactivities of GRP, this entity may be an important hormone during ovine fetal life.

Light- and electron-microscopic immunochemical analysis of nerve fibre types innervating the taenia of the guinea-pig caecum.

The present work was undertaken to determine by immunocytochemical methods which of the putative enteric neurotransmitters are contained in axons supplying the guinea-pig taenia coli and what proportion of axons is accounted for by the presence of these substances. Numerous fibres displayed immunoreactivity for dynorphin (DYN), enkephalin (ENK), gamma-aminobutyric acid (GABA), nitric oxide synthase (NOS), substance P (SP) and vasoactive intestinal peptide (VIP), but, in contrast to other gut regions, fibres showing immunoreactivity for gastrin-releasing peptide, galanin and neuropeptide Y were rare in the taenia. Fibres reactive for calbindin, calcitonin gene-related peptide, cholecystokinin, 5-hydroxytryptamine and somatostatin were also rare. Tyrosine hydroxylase-like immunoreactivity (TH-LI) was present in numerous fibres that disappeared after extrinsic denervation, a procedure that did not detectably affect any of the other major groups of fibres. Simultaneous staining of extrinsically denervated preparations revealed that SP-LI and VIP-LI were located in separate fibres, and ultrastructural studies showed these to be 58% and 33% of intrinsic fibres supplying the muscle. Immunoreactivity for the general marker, neuron-specific enolase, was located in 95-98% of axons. ENK-LI and DYN-LI were in the same axons, and similar proportions of the fibres with either SP-LI or VIP-LI, about 85%, contained immunoreactivity for ENK and DYN. All VIP-LI fibres, but no SP-LI fibres, were reactive for NOS. The results imply that the taenia of the guinea-pig caecum is innervated by two major groups of enteric neurons: (i) excitatory neurons that contain ACh, SP, other tachykinins, and, in most cases, DYN-LI and ENK-LI; and (ii) inhibitory neurons that contain NOS-LI, VIP-LI, in most cases, the two opioids and, quite probably, ATP as a transmitter. GABA-LI is contained in a smaller population of intrinsic axons. Even though the taenia represents one of the simplest tissues for examining transmission from enteric neurons to intestinal muscle, it shares some of the complexity of other regions, in that four major axon types supply the muscle and both the enteric excitatory and enteric inhibitory neurons contain multiple transmitters.

Gastrin releasing peptide immunoreactivity (GRP-IR) is present in amniotic fluid and fetal and maternal circulations of sheep

Gastrin releasing peptide immunoreactivity (GRP-IR) is present in amniotic fluid and fetal and maternal circulations of sheep

The secretory granule peptides 7B2 and CCB are sensitive biochemical markers of neuro‐endocrine bronchial tumours in man

Bronchial tumours are the most frequent cause of the ectopic ACTH syndrome. Two types of tumours are classically responsible: the relatively benign carcinoids and the highly aggressive small cell carcinomas. Both have neuro-endocrine features and are thought to originate from the endocrine component of the bronchial tree. Our objective was to assess the sensitivity of 7B2 and secretogranin 1 as new biochemical markers of neuro-endocrine differentiation in these tumours in comparison with gastrin releasing peptide. Tissue concentration of 7B2, secretogranin 1 fragments (GAWK and CCB), gastrin releasing peptide and beta-endorphin were measured in normal human lung (n = 4), bronchial carcinoid tumours with (n = 5) and without (n = 15) the ectopic ACTH syndrome, small cell carcinomas (n = 2), squamous cell carcinomas (n = 11) and adenocarcinomas (n = 6). Molecular weight forms of immunoreactive--ACTH, -GAWK, -gastrin releasing peptide, and -7B2 were also examined using gel exclusion chromatography and Western blot analysis. We detected 7B2 immunoreactivity in 19 of 22 neuro-endocrine lung tumours (with values ranging from less than 5 to 555 fmol/mg wet weight tissue), CCB immunoreactivity in 20 of 22 tumours with neuro-endocrine features (with values ranging from less than 5 to 19,875 fmol mg wet weight tissue) and gastrin releasing peptide immunoreactivity in 10 of 22 neuro-endocrine lung tumors (with values ranging from less than 5 to 11,132 fmol/mg wet weight tissue). Immunoreactive 7B2 and CCB were detected neither in tumours with non-endocrine features, nor in the four normal lung specimens. Differing molecular weight forms of immunoreactive 7B2 in two bronchial carcinoids associated with the ectopic ACTH syndrome showed a predominant signal corresponding to a molecular weight of 22 kDa; in addition, a second signal of 19 kDa was also present. The differing molecular weight forms of immunoreactive ACTH related peptides in the five tumours responsible for the ectopic ACTH syndrome showed, in addition to ACTH1-39, the constant presence in variable proportions of corticotrophin-like intermediary lobe peptide (or ACTH18-39). The differing molecular weight forms of immunoreactive GAWK showed heterogeneous results with materials eluting at Kav of 0, 0.3 and 0.4 respectively. In the three bronchial carcinoids studied, two immunoreactive gastrin releasing peptide molecular weight forms were always found at Kav of 0.5 and 0.85 corresponding to gastrin releasing peptide and its fragment 14-27 respectively. Our results show that 7B2 and the two fragments of secretogranin 1 (GAWK and CCB) are the best biochemical markers of neuro-endocrine differentiation in human lung tumours.

Evidence for the presence of gastrin-releasing peptide immunoreactivity in rat anterior pituitary corticotrophs and lactotrophs, AtT20 cells, and GH3 cells: failure to demonstrate participation in local control of hormone release.

Using antisera raised against the N-terminal (1-16) or the C-terminal part of the bombesin (BBN)-like peptide gastrin-releasing peptide (GRP) and against the C-terminus of pro-GRP, GRP- and pro-GRP-like immunoreactivity (IR) was detected by immunostaining in freshly dispersed rat anterior pituitary (AP) cells and in reaggregate AP cells cultured in serum-free medium. Depending on the antiserum used, 6.4 +/- 0.4% to 12.4 +/- 2.7% of freshly dispersed cells were immunoreactive. Solid phase preabsorption of the antisera with the respective antigens abolished the staining. GRP-IR was detectable by double immunostaining in a subpopulation of PRL cells and ACTH-containing cells. In contrast, only very few somatotrophs, gonadotrophs, and thyrotrophs were immunoreactive, and they were much smaller than the typical mature forms of these cell types. GRP- and pro-GRP-IR were also detected in the ACTH-secreting AtT20 cell line and in the PRL- and GH-secreting GH3 cell line. GRP- and pro-GRP-IR were present in AP cell aggregates maintained in culture for 4 weeks. The finding of both GRP- and pro-GRP-IR in a subpopulation of lactotrophs and corticotrophs and their persistence in culture under serum-free conditions strongly suggest that GRP-like peptides are produced in rat AP. Although the potent GRP receptor antagonist L 686,095-001C002 effectively blocks stimulation of GH and PRL release by exogenous BBN-like peptides, it failed to affect basal GH and PRL release from perifused reaggregate AP cell cultures as well as GH and/or PRL release stimulated by epinephrine, vasoactive intestinal peptide, TRH, GH-releasing factor, and angiotensin-II or PRL release inhibited by dopamine. Thus, the latter data do not support the hypothesis often suggested that peptides endogenously present in AP cells are involved in the paracrine regulation of AP hormone secretion.

GRP(Gastrin-Releasing Peptide)-Containing Nerves in the Rat Stomach and Stress-Induced Depletion of Their Synaptic Vesicles. An Electron Microscope Study.

Gastrin-releasing peptide (GRP)-containing nerves are extremely numerous in the mucosa of the gastric body. Our previous study demonstrated that depletion of GRP from the nerves occurred in close relation to ulceration in the stomach. The present study deals with the ultrastructure of the GRP-immunoreactive nerves under normal conditions and its changes induced by conditions of stress. The immunoreactivity for GRP was recognized selectively in large cored vesicles in the swollen axoplasm of the nerves. The same axoplasm further revealed immunonegative small clear vesicles which were believed to contain acetylcholine. In materials where the GRP-immunoreactive nerves markedly decreased in number, both large and small synaptic vesicles were depleted from the nerves. These findings suggest that GRP and acetylcholine coexist in single nerves in the oxyntic mucosa, and that by nerve stimulation, they are coreleased into the lamina propria.

Bombesin-like Peptides: From Frog Skin to Human Lung

The tetradecapeptide bombesin was first isolated from the skin of the frog Bombina bombina by Erspamer and col­ leagues in 1970 (1). Since then, similar peptides have been demonstrated in other amphibia, mammals, avians, fish, and invertebrates. The group of bombesin-like peptides is de­ fined by a region of homology at the carboxyl-terminus, in which resides their biologic activity. Due to this homology, physiologic and immunologic properties of these peptides of­ ten overlap. Bombesin binds to a cell surface receptor and initiates a number of early events, including inositol triphos­ phate and diacylglycerol accumulation, protein kinase C ac­ tivation, Ca+ 2 mobilization, Na' influx and Na+/H+ antiport, arachidonic acid release, cAMP accumulation, and elevation of c-mycand e-fosmRNA levels (2). Bombesin and its mam­ malian homologue, gastrin-releasing peptide (GRP), have a number of actions that are of interest, including mitogenesis for fibroblasts, epithelial cells, and small cell lung cancer, bronchoconstriction, vasodilation, the promotion of mucous secretion, regulation of gastrin release, monocyte chemo­ taxis, and appetite suppression (3). In humans, the fully characterized bombesin-like peptides include GRP and neuromedin B, analogous to the amphibian peptides bombesin and ranatensin, respectively (4, 5). Neu­ romedin B is reported to be largely confined to neural tissue, whereas GRP is synthesized in isolated neuroendocrine cells as well as in the nervous system. Bombesin-like immuno­ reactivity has also been reported in macrophages, but there has been no demonstration of GRP mRNA in this cell type (6). Thus, it is possible that macrophages may either take up GRP from their environment or synthesize GRP or a related peptide. GRP mRNA and immunoreactivity have been studied in human fetal lung development (7). GRP-positive neuroendo­ crine cells are first demonstrated at the end of the first trimes­ ter and increase in number until shortly after birth. GRP­ positive neuroendocrine cells are prominent in the develop­ ing airways and follow a centrifugal pattern that parallels the morphogenesis of the fetal airways. Little direct evidence ex­ ists to define a role for GRP in fetal lung development, al

Production of Gastrin-Releasing Peptide-(18-27) and a StaWe Fragment of Its Precursor in Small Cell Lung Carcinoma Cells*

The production and postsecretory stability of gastrin-releasing peptide (GRP) and the C-terminal part of the GRP precursor were studied in small cell lung cancer cell lines using RIAs developed against these two parts of the precursor. In three otherwise different cell lines (NIC-H345, NIC-H69, and NIC-H510), similar chromatographic patterns of mainly GRP-(18-27) and some GRP-(14-27) along with large fragments of the C-terminal counterpart of the precursor were found to be stored in the cells. In tissue culture medium, gel filtration chromatography indicated that postsecretory limited proteolysis of the GRP precursor fragments occurred. The amount of accumulated immunoreactivity varied among the three cell lines and between the two parts of the precursor. In medium in which only low amounts of GRP immunoreactivity accumulated, the radiolabeled GRP was degraded rapidly. When incubated with plasma, GRP-(14-27) disappeared within a few hours, whereas the C-terminal precursor fragments were stable. It is concluded that the postsecretory stability of peptides excised from the GRP precursor in small cell lung cancer cells varies under tissue culture conditions, but epitopes in the C-terminal part of the precursor are more stable in plasma than the small GRP peptides and, thus, may serve as a better indicator than GRP itself for expression of the GRP precursor in cancer cells.

Projections of chemically-specified neurons in the guinea-pig colon.

The arrangement of the enteric nerve plexuses in the colon of the guinea-pig and the distributions and projections of chemically specified neurons in this organ have been studied. Immunoreactivity for neuron specific enolase was used to examine the total population of neurons and individual subpopulations were studied using antibodies raised against calbindin, calcitonin gene-related peptide (CGRP), leu-enkephalin, gastrin releasing peptide (GRP), galanin, gamma aminobutyric acid, neurokinin A, neuropeptide Y (NPY), somatostatin, substance P, tyrosine hydroxylase and vasoactive intestinal peptide (VIP). Neuronal pathways within the colon were lesioned using myotomy and myectomy operations and extrinsic pathways running between the inferior mesenteric ganglia and the colon were also severed. Each of the antibodies revealed nerve cells and nerve fibres or only nerve fibres within the wall of the colon. VIP, galanin and GRP were in anally projecting pathways in the myenteric plexus, as they are in other species. In contrast, there are differences in the projection directions of enkephalin, substance P, NPY and somatostatin nerve fibres between regions and species. Surprisingly, somatostatin and NPY fibres have opposite projections in the small intestine and colon of the guinea-pig. The majority of nerve fibres that innervate the circular muscle, including fibres with immunoreactivity for VIP, enkephalin, substance P, NPY, galanin and GRP come from the myenteric ganglia. The mucosa is innervated by fibres from both the myenteric and submucous ganglia. The present results suggest that the guinea-pig distal colon is a suitable place in which to determine relations between structure, neurochemistry and functions of enteric neural circuits.

Characterization of gastrin-releasing peptide immunoreactivity in distinct storage particles in guinea pig myenteric and Torpedo electromotor neurones

Using high resolution centrifugal density-gradient separation of cytoplasmic extracts of guinea pig myenteric plexus and Torpedo electric tissue, we have succeeded in isolating fractions of storage particles rich in gastrin-releasing peptide (GRP). In extracts of myenteric plexus and gradients derived therefrom, the 10-amino acid GRP peptide (GRP-10) was the sole form present; this was bimodally distributed in the gradients, one peak copurifying with Golgi membranes and apparently consisting of immature storage particles, the other with other synaptophysin-rich neuropeptide-containing particles. In extracts of electric organ, a tissue rich in cholinergic electromotor nerve terminals, and gradients derived therefrom, GRP-like immunoreactivity behaved in gel permeation and reversed phase high performance liquid chromatography like the 27-amino acid peptide (GRP-27). About half of the immunoreactivity sedimented in the centrifugal gradient to a region rich in particles containing vasoactive intestinal polypeptide-like immunoreactivity; the remainder was recovered in a very dense region of the gradient containing larger membrane fragments, including synaptosomes. The electromotor nerves and cell bodies also contained GRP-27-like immunoreactivity in relatively high concentration as did the Torpedo gut. It is concluded that this GRP-like peptide is packaged in dense storage particles in the electromotor neurones.

Gastrin-releasing peptide-like immunoreactivity in porcine follicular fluid and ovary

Porcine follicular fluid was found to contain gastrin-releasing peptide (GRP) by radioimmunoassay. High pressure liquid chromatography of the extracted material showed two peaks of GRP immunoreactivity that closely resembled the C-terminal fragments of GRP, GRP18-27 and GRP14-27. Immunohistochemical studies revealed specific staining for GRP in the granulosa cells of adult porcine ovary. These results demonstrate the presence of substances which behave like authentic GRP-like peptides in porcine ovary and follicular fluid and suggest that these peptides may play a paracrine and/or autocrine role in the regulation of the ovarian function.

Identification of immunoreactive gastrin-releasing peptide related substances in adult rat Leydig cells.

Purified adult rat Leydig cells were found to produce gastrin-releasing peptide (GRP) by radioimmunoassay (RIA). Gel chromatography of the extracted material showed a single peak of GRP immunoreactivity. Further high pressure liquid chromatography (HPLC) analysis resolved the extract into two peaks that closely resembled the C-terminal fragment of GRP, GRP18-27 and GRP14-27. Immunohistochemical studies revealed specific staining for GRP in the Leydig cells of adult rat testis. These results demonstrate, by a number of independent criteria, that rat Leydig cells contain substances which behave like authentic GRP-like peptides. Since the peptides appear to be of local origin, a paracrine function within the rat testis is suggested.

Gastrin-releasing peptide (GRP) immunoreactivity in the rat retina: A radioimmunoassay, immunohistochemical and chromatographic study

Using radioimmunoassay, reverse phase high pressure liquid chromatography (rp HPLC) and immunohistochemistry, we have identified gastrin releasing peptide-immunoreactivity (GRP-IR) in the rat retina. The concentration of GRP-IR in retinal extracts was 7.4 ± 0.6 ng/g wet wt. (mean ± S.E.M. n = 15). There was no significant difference between the levels of immunoreactivity in 12-h light and 12-h dark adapted retinae. rp HPLC analysis of retinal extracts demonstrated that two main immunoreactive components were present which corresponded in retention time to GRP 10 (neuromedin C) and GRP 14 (GRP 14–27). A small amount of material also co-eluted with GRP 27. Using immunohistochemistry, the immunoreactivity has been localised in the inner retinal layers. Immunoreactive somata were present in the proximal inner nuclear layer and in the ganglion cell layer. Fibre staining was present in laminae 2 and 4 of the inner plexiform layer. Somatal staining was increased by pretreatment of retinae with vincristine while the laminar staining was markedly reduced. These results demonstrate the existence of GRP-like peptides in the rat retina which has not previously been reported.

<b>GASTRIN-RELEASING PEPTIDE (GRP)-CONTAINING NEURONS IN THE RAT OXYNTIC MUCOSA VVITH SPECIAL REFERENCE TO EXPERIMENTALLY INDUCED PEPTIC </b><b>ULCERS </b>

The relation between gastrin-releasing peptide (GRP)-immunoreactive nerves and development of stomach ulcers was studied in rats. The ulcer was induced by exposure of animals to restraint plus water immersion or by administration of insulin, serotonin, aspirin, indomethacin or ethanol. Immunohistochemistry demonstrated a network of nerves exhibiting the immunoreactivity for GRP in the oxyntic mucosa of normal animals. A marked decrease in number of the GRP-immunoreactive nerves was seen to accompany with the ulcers induced by the restraint stress or by insulin. On the other hand, no appreciable change in number of the GRP-immunoreactive nerves was found in ulcers induced by indomethacin, serotonin, ethanol or aspirin. Vagotomy prevented not only the development of ulcers by stress or insulin, but also the decrease in the GRP-immunoreactive nerves. Electrical stimulation of the vagal nerve resulted in ulcer formation and also caused a marked decrease in number of the GRP-immunoreactive nerves in the oxyntic mucosa. The results suggest the possibility that depletion of GRP from nerves in the oxyntic mucosa may be involved in the development of stress or insulin ulcers and that such a release of GRP may be caused by hyperactivity of the vagal nerve.

Depletion of gastrin-releasing peptide(GRP) from nerves in the gastric body of rats with experimental ulcers. An immunohistochemical study.

A predominant population of mucosal nerves in the mammalian gastric body has been known to contain large amounts of gastrin-releasing peptide (GRP). The present immunohistochemical study demonstrates the depletion of GRP immunoreactivity from nerves in the oxyntic mucosa of rats with ulcers induced by restraint plus water immersion. Depletion of GRP occurred in a major part of the nerves after 3 h exposure to the stress, and after 6 h exposure only a few nerve fibers could be recognized. In contrast, GRP fibers in the pyloric mucosa did not decrease significantly in number in any of the stressed rats. Since the depletion of GRP immunoreactivity preceded mucosal erosion in the gastric body, the possibility is proposed that GRP released from the nerves may be related to stress-related ulceration in the stomach.

Synaptic relationships between neurons containing vasopressin, gastrin-releasing peptide, vasoactive intestinal polypeptide, and glutamate decarboxylase immunoreactivity in the suprachiasmatic nucleus: dual ultrastructural immunocytochemistry with gold-substituted silver peroxidase.

In order to examine the morphological substrates for neuronal connections between cells of the hypothalamic suprachiasmatic nucleus (SCN) that contain immunoreactivity for different neurotransmitters, a double ultrastructural immunocytochemical analysis was used. For double immunostaining, the first neuroactive substance antigen was labeled with gold-substituted silver-intensified peroxidase (GSSP), which results in a granular gold deposit of high electron and light opacity. The second antigen was labeled with peroxidase and a diaminobenzidine chromagen. The GSSP reaction product greatly increased the visibility of immunoreactive structures, with both light and electron microscopy. Intensification with the GSSP method worked at all depths of thick tissue sections as determined with analysis of immunostained sections cut perpendicular to their flat surface, and with analysis of thick 80-micron sections of brain tissue into which horseradish peroxidase (HRP) has been microinjected. On a nitrocellulose dot-blot comparison of different substrates for HRP, the GSSP intensification compared favorably with tetramethylbenzidine, but unlike tetramethylbenzidine, the GSSP was stable in a wide range of buffers. In addition to diaminobenzidine, the GSSP reaction was used to intensify and stabilize both the Hanker-Yates reagent and tetramethylbenzidine on the nitrocellulose model system. Through the use of the GSSP reaction, five new synaptic relationships in the suprachiasmatic nucleus were revealed. By increasing the sensitivity of the peroxidase method by silver-gold intensification, immunoreaction product could be found in dendrites at a greater distance from the perikaryon than in nonintensified material. Because of this greater sensitivity, the neuroactive substance contained in the cell of origin of a dendrite could sometimes be identified. Boutons immunoreactive for vasopressin-associated neurophysin were found to make synaptic contact with postsynaptic dendrites that also contained vasopressin-neurophysin immunoreactivity. Similarly, boutons containing gastrin-releasing peptide immunoreactivity made synaptic contact with cells also exhibiting gastrin-releasing peptide immunoreactivity. Neurons stained with GSSP reaction product could be easily discriminated from those containing only HRP-precipitated diaminobenzidine, allowing the simultaneous use of these two markers in the same 30-micron tissue section and subsequently in ultrathin sections for electron microscopy.(ABSTRACT TRUNCATED AT 400 WORDS)

Two prohormones for gastrin-releasing peptide are encoded by two mRNAs differing by 19 nucleotides.

In our studies on the molecular biology of human gastrin-releasing peptide (GRP), we have discovered an example of a change in translational reading frame apparently produced through alternative RNA splicing. Complementary DNAs prepared from a pulmonary carcinoid tumor rich in GRP immunoreactivity had one of two different-sized internal DNA fragments after digestion with the restriction enzyme Pvu II. Nucleotide sequences of the two DNA fragments were identical except for 19 additional nucleotides present in the larger fragment. The region of the mRNA containing the 19 nucleotides corresponded to the carboxyl-terminal region of the human GRP precursor. The resulting shift in reading frame causes a difference of 10 amino acids in size and an overall sequence difference of 27 amino acids between the two GRP prohormones so formed. The change in reading frame described here is unusual in eukaryotes and is yet another mechanism to produce diversity in the generation of biological peptides.

Gastrin releasing peptide in human neuroendocrine tumours.

Neuroendocrine tumours of the lung and gut are known to possess bombesin-like immunoreactivity. The recent observation that gastrin releasing peptide (GRP), a 27 amino acid peptide isolated from the porcine intestine, may be the mammalian analogue of bombesin led us to look for this peptide in a variety of human neoplasms. Formalin-fixed tissues from 85 tumours were examined by the immunoperoxidase technique, using specific antisera to the GRP molecule (1-27) and the GRP fragment (1-16). Intense cytoplasmic GRP immunoreactivity was seen in thyroid medullary carcinomas (3/3), carcinoids of lung, pancreas, and intestine (22/36), and paragangliomas (2/3). Less frequent staining was present in pulmonary small cell (oat cell) carcinomas (1/8) and pituitary adenomas (1/6). Complete absence of immunoreactivity was observed in three phaeochromocytomas, five Merkel cell tumours, six neuroblastomas and 15 non-neuroendocrine tumours. Normal neuroendocrine cells of the thyroid (C-cells) and bronchial mucosa (Kulchitsky cells) exhibited GRP immunoreactivity; nerve fibres from all sites failed to demonstrate staining for GRP. In each positive case, the pattern of staining for GRP (1-27) and GRP (1-16) was identical, although the GRP (1-16) immunostaining was weaker. These findings indicate that bombesin immunoreactivity in human neuroendocrine cells and tumours is attributable to GRP-like molecules and that GRP is a useful marker of neuroendocrine differentiation in many tumours.

Gastrin-releasing peptide immunoreactivity in intestinal carcinoids.

Human neuroendocrine tumors are known to demonstrate immunoreactivity to the amphibian peptide bombesin. The recent observation that gastrin-releasing peptide (GRP), a 27 amino acid peptide first isolated from porcine intestine, may be the mammalian analog of bombesin led us to look for this peptide in intestinal carcinoid tumors. Formalin-fixed tissues from 20 of these tumors were examined by the immunoperoxidase technic, using specific antisera to the GRP molecule (1-27) and the GRP fragment (1-16). Intense diffuse cytoplasmic immunoreactivity was observed in carcinoids from the small intestine (7/10), appendix (4/5), and colon (1/5). In each positive case, the pattern of staining for GRP (1-16) and GRP (1-27) was identical. These findings indicate that bombesin-like immunoreactivity in human intestinal carcinoid tumors is attributable to GRP-like molecules and that GRP is a useful marker for neuroendocrine differentiation.