Pancreastatin-dependent inflammatory signaling mediates obesity-induced insulin resistance.

Chromogranin A knockout (Chga-KO) mice exhibit enhanced insulin sensitivity despite obesity. Here, we probed the role of the chromogranin A-derived peptide pancreastatin (PST: CHGA(273-301)) by investigating the effect of diet-induced obesity (DIO) on insulin sensitivity of these mice. We found that on a high-fat diet (HFD), Chga-KO mice (KO-DIO) remain more insulin sensitive than wild-type DIO (WT-DIO) mice. Concomitant with this phenotype is enhanced Akt and AMPK signaling in muscle and white adipose tissue (WAT) as well as increased FoxO1 phosphorylation and expression of mature Srebp-1c in liver and downregulation of the hepatic gluconeogenic genes, Pepck and G6pase. KO-DIO mice also exhibited downregulation of cytokines and proinflammatory genes and upregulation of anti-inflammatory genes in WAT, and peritoneal macrophages from KO mice displayed similarly reduced proinflammatory gene expression. The insulin-sensitive, anti-inflammatory phenotype of KO-DIO mice is masked by supplementing PST. Conversely, a PST variant peptide PSTv1 (PST-NΔ3: CHGA(276-301)), lacking PST activity, simulated the KO phenotype by sensitizing WT-DIO mice to insulin. In summary, the reduced inflammation due to PST deficiency prevented the development of insulin resistance in KO-DIO mice. Thus, obesity manifests insulin resistance only in the presence of PST, and in its absence obesity is dissociated from insulin resistance.

Aire-dependent alterations in medullary thymic epithelium indicate a role for Aire in thymic epithelial differentiation.

The prevalent view of thymic epithelial differentiation and Aire activity holds that Aire functions in terminally differentiated medullary thymic epithelial cells (MTECs) to derepress the expression of structural tissue-restricted Ags, including pancreatic endocrine hormones. An alternative view of these processes has proposed that Aire functions to regulate the differentiation of immature thymic epithelial cells, thereby affecting tissue-restricted Ag expression and negative selection. In this study, we demonstrate that Aire impacts several aspects of murine MTECs and provide support for this second model. Expression of transcription factors associated with developmental plasticity of progenitor cells, Nanog, Oct4, and Sox2, by MTECs was Aire dependent. Similarly, the transcription factors that regulate pancreatic development and the expression of pancreatic hormones are also expressed by wild-type MTECs in an Aire-dependent manner. The altered transcriptional profiles in Aire-deficient MTECs were accompanied by changes in the organization and composition of the medullary epithelial compartment, including a reduction in the medullary compartment defined by keratin (K) 14 expression, altered patterns of K5 and K8 expression, and more prominent epithelial cysts. These findings implicate Aire in the regulation of MTEC differentiation and the organization of the medullary thymic compartment and are compatible with a role for Aire in thymic epithelium differentiation.

Characterisation of WE-14 in porcine ocular tissue.

WE-14 is derived from the cell-specific posttranslational processing of chromogranin A (CgA) in subpopulations of neuroendocrine cells and neurons. Region- and site-specific chromogranin A, pancreastatin and WE-14 antisera were employed to study the generation of WE-14 in porcine ocular tissues. No chromogranin A or pancreastatin immunostaining was detected in ocular tissue. Immunohistochemistry detected WE-14 immunostaining in a network of nerve fibre bundles and nerve fibres throughout the limbus, cornea, iris and ciliary body with sparse nerve fibres detected throughout the choroid and sclera. Retinal analysis detected intense WE-14 immunostaining in large ovoid cells in the ganglion cell layer with weak immunostaining in a population of small cells in the inner nuclear layer; weak immunostaining was detected within the fibre layers in the inner plexiform layer. Quantitatively, the highest WE-14 tissue concentration was recorded in aqueous retinal and corneal extracts with lower concentrations in the sclera, choroid and anterior uveal tissues. Chromatographic profiling resolved a minor chromogranin A-like immunoreactant and a predominant immunoreactant co-eluting with synthetic human WE-14. This is the first study to demonstrate that WE-14 is generated in neuronal fibres primarily innervating the anterior chamber and in select cell populations in the retina.

Low nuclear proliferative activity is associated with nonmetastatic islet cell tumors.

CONTEXT: Traditional morphologic features of tumor aggression are of limited value in predicting the malignant behavior of endocrine neoplasms. We explored the potential value of nuclear proliferative activity (using Ki-67 immunostaining with semiquantitative scoring) in predicting the clinical behavior of pancreatic islet cell tumors (ICTs), and we correlated this characteristic with hormone expression. OBJECTIVE: To evaluate whether Ki-67 immunostaining using a semiquantitative scoring system has value in predicting the clinical behavior of pancreatic ICTs. DESIGN: We studied 39 pancreatic ICTs from 39 patients. Twenty-two ICTs did not metastasize in a median follow-up period of 91 months. The remaining 17 neoplasms did produce metastases (8 in liver, 7 in regional lymph nodes, and 2 in peritoneum). Immunohistochemistry was performed using antibodies to Ki-67 and pancreatic hormones (insulin, glucagon, gastrin, somatostatin, pancreatic polypeptide, vasoactive intestinal polypeptide, and corticotropin). A semiquantitative Ki-67 grading system was followed. The nuclear proliferative activity, as determined by a positive reaction for Ki-67, was considered low (<5% of cells staining positively), intermediate (5%-25% of cells staining positively), or high (>25% of cells staining positively). RESULTS: The majority of the nonmetastatic ICTs (16 cases, 73%) demonstrated either negative or low staining for Ki-67 (P <.001). Conversely, all metastatic ICTs expressed at least an intermediate-grade reaction. High nuclear proliferative activity was only seen in metastatic neoplasms (3 cases, 17%). There was no relationship between immunoexpression of pancreatic hormones and nuclear proliferative activity by either group of tumors. CONCLUSION: An ICT with low nuclear proliferative activity is unlikely to metastasize, whereas high proliferative activity is associated with a metastatic phenotype. Immunohistochemical assessment of Ki-67 using a semiquantitative scoring system is a simple and reliable detection method of cellular proliferative activity in ICTs of the pancreas.

Immunohistochemical expression of transforming growth factor alpha and epidermal growth factor receptor in pancreatic endocrine tumors.

Coexpression of transforming growth factor alpha (TGF-alpha) and its receptor epidermal growth factor receptor (EGFR) is known to be associated with aggressive biologic behavior and adverse clinical outcome in a variety of tumors, including pancreatic adenocarcinomas. However, very little information is currently available as to whether this is true of pancreatic endocrine tumors (PETs) as well. Thirty-five PETs were retrospectively studied for immunohistochemical expression of TGF-alpha, the intracellular and extracellular domains of EGFR, and various hormonal secretory products. Proliferative activity was additionally studied (in 20 cases only) using the MIB-1 antibody. Thirty-one (89%) of 35 tumors were reactive for 1 or more of the peptide hormones tested; 22 (63%) tumors were positive for TGF-alpha; and 23 (65%) were positive for the intracellular and/or extracellular domain of EGFR. Based on their TGF-alpha and EGFR expression, these tumors could be classified into 4 groups. Of the 10 tumors in group I (positive for TGF-alpha and the complete EGFR molecule), 3 were malignant, 6 were >2 cm in diameter, 5 were functional, and 1 had a proliferative index of >40%. The 12 tumors in group II (positive for TGF-alpha but negative for the intracellular and/or extracellular domain of EGFR) included 4 malignant tumors, 4 PETs >2 cm in diameter, 8 functional, and 1 with a proliferative index of >40%. The 7 PETs in group III (positive for the intracellular/extracellular domain of EGFR alone) included 3 malignant tumors, 3 PETs >2 cm in diameter, and 3 functional tumors. The 6 tumors in group IV (completely negative for both TGF-alpha and EGFR) included 4 malignant tumors, 3 PETs >2 cm in diameter, and 4 functional lesions. Therefore, immunohistochemical expression of TGF-alpha and EGFR, either alone or in concert, shows no correlation with size, functional status, secretory profile, or biologic behavior and hence cannot be used as a marker of malignancy in this group of tumors.

Carcinoid tumors of the duodenum and ampulla of vater: a clinicomorphologic, immunohistochemical, and cell kinetic comparison.

Carcinoid tumors of the ampulla of Vater (ACs) differ from duodenal carcinoid tumors (DCs). A search for AC and DC was made between 1980 and 2000. The clinicopathologic features and follow-up were assessed. Immunohistochemistry for panneuroendocrine markers, hormone products, proliferating cell nuclear antigen (PCNA), Ki- 67, p21(cip1), and p27(kip1) were performed. A blind proliferative index counting 500 cells was made. Differences were contrasted using the Fisher exact and 2-sided Student t test. Five ACs and 8 DCs were identified in 9 women and 4 men with median ages of 59 and 64 years and mean tumor diameters of 1.6 and 1.85 cm, respectively. All patients with AC presented jaundice, and most patients with DC were asymptomatic (P = .047). Metastases were present in 4 ACs and 1 DC (P =.03). Tumor cells expressed synaptophysin and chromogranin in 60% of ACs and in 100% and 87% of DCs. Gastrin was expressed in 75% of DCs and 20% of ACs (P < .05). The mean value for PCNA index was 4.0% in ACs and 3.2% in DCs, and mean values for Ki-67 were 12.2% and 10.2%, respectively (P = NS). Expression of p21(cip1) and p27(kip1) was observed in 40% of ACs and 37.5% and 12.5% of DCs. Three of 5 patients with AC died of the disease within an average of 11 months, and none of the patients with DC had died at 103 months of follow-up. The more aggressive behavior of ACs is not associated with higher proliferative indices or with different expression of cell cycle inhibitors.

Chromogranin-B regulation of IAPP and insulin secretion.

In the endocrine pancreas, chromogranin-A and pancreastatin have been suggested to inhibit islet insulin secretion, whereas chromogranin-B has not been studied in this context. Furthermore, a putative effect by chromogranins on IAPP secretion is unknown. We aimed to elucidate the endogenous effect of chromogranin-A, pancreastatin and chromogranin-B on islet insulin and IAPP secretion from pancreatic NMRI mouse islets. In acute experiments, there was a tendency towards an increase in insulin release, which became more manifest after a 48-h exposure. Moreover, 48 h exposure to chromogranin-B antiserum resulted in a significant increase in (pro)insulin synthesis. Neither antibodies against chromogranin-A nor pancreastatin had any effect on islet hormone secretion. None of the antibodies tested had any effect on islet IAPP or insulin content. We suggest that chromogranin-B released from islets may have an autocrine inhibitory effect on islet IAPP and insulin secretion. Our data imply a regulatory role of chromogranin-B in islet IAPP and insulin secretion.

Distribution of calcitonin-gene-related peptide, neuropeptide-Y, vasoactive intestinal polypeptide, cholecystokinin-8, substance P and islet peptides in the pancreas of normal and diabetic rats.

Neuropeptides and peptides are particularly important in the co-ordination of pancreatic exocrine and endocrine secretions. In diabetes mellitus, pancreatic endocrine secretion is particularly impaired. This study investigates whether there is a change in the pattern of distribution of neuropeptides including calcitonin-gene-related peptide (CGRP), neuropeptide-Y (NPY), vasoactive intestinal polypeptide (VIP), cholecystokinin-octapeptide (CCK-8), substance P (SP), and islet peptides including insulin (INS), glucagon (GLU), somatostatin (SOM) and pancreatic polypeptide (PP) in the pancreas of streptozotocin (STZ)-diabetic rats. After the onset of diabetes, the pattern of distribution of INS, GLU, SOM and PP cells was deranged. CGRP was demonstrated in ganglion cells of both normal and diabetic pancreas. CGRP was also localized in nerve fibres innervating the blood vessels of both normal and diabetic pancreas. The pancreata of both normal and diabetic rats contained numerous NPY-immunopositive varicose nerve fibres in the wall of blood vessels. In normal pancreatic tissue, VIP-immunopositive nerve fibres were observed in all areas of the pancreas. After the onset of diabetes, VIP-positive nerve fibres were still discernible in the interacinar regions of the pancreas. CCK-8 was identified in nerve fibres innervating both the normal and diabetic rat pancreata. These CCK-8-immunopositive nerves were varicose in nature and distributed in the wall of blood vessels. SP was demonstrated in neurons located in the interlobular areas of normal tissue and in fine varicose nerve fibres of the interacinar region of STZ-induced diabetic pancreas. In conclusion, CGRP, NPY, VIP, CCK-8 and SP are well distributed in both normal and diabetic pancreas.

Prenatal development of the human pancreatic islets. Immunocytochemical identification of insulin-, glucagon-, somatostatin- and pancreatic polypeptide-containing cells.

Histological studies were performed on 24 pancreases of normal human embryos and fetuses aged 7 to 38 weeks. For immunocytochemistry, the avidin-biotin-peroxidase method was used to identify and localize insulin, glucagon, somatostatin, and pancreatic polypeptide (PP) cells. In 7 wk old embryos, cells containing somatostatin and PP are observed. One week later appear single glucagon-positive cells. In the 9th wk, insulin producing cells are visible. During the fetal period two populations of the investigated cells are found: Langerhans islets and dispersed cells. The latter cells containing insulin, glucagon or somatostatin are localized in the walls of pancreatic ducts throughout the whole gland, while PP-positive cells are seen mainly in the part of the pancreas, which develops from the ventral anlage (anteroinferior part of the head and adjacent part of the main pancreatic duct). During the development of islets we have observed four stages: (1) scattered cells (7 to 10 weeks); (2) grouping cells (11 to 15 weeks); (3) mantle and zonular islets (10 to 29 weeks), in which B cells located inside are surrounded by a thick zone of A, PP and somatostatin-producing cells; (4) mixed islets (from 30 weeks on) - all cells are scattered over the whole transverse section of the islet. In the developing pancreas, the glucagon- and somatostatin-containing cells are the most numerous, while the insulin and PP-containing cells occur in lesser quantities.

Chromogranin A and pancreastatin-like immunoreactivity in normal pregnancies.

Placenta is a neuroendocrine organ, and we therefore wanted to study the occurrence of the general neuroendocrine marker chromogranin A (CgA) and its split product pancreastatin. CgA and pancreastatin-like immunoreactivity (PST-LI) were determined by ELISA and RIA methods, respectively, in homogenates from term placentas, sera from pregnant women, nonpregnant women, umbilical cords, and in amniotic fluids. In placental homogenates, the mean level of CgA was 7.1 +/- 8.6 pmol/g wet wt (mean +/- SD), whereas PST-LI was not detectable. CgA immunoreactivity was demonstrated by immunofluorescence studies of isolated trophoblasts and decidual cells from term placentas. In trophoblasts, CgA was colocalized with human chorionic gonadotropin (hCG) and human placental lactogen. By Northern blotting, a distinct band corresponding to CgA messenger RNA (mRNA) was demonstrated in the placental cell line, whereas, in placental homogenates, a mRNA band of a slightly larger size was found. Median CgA level in maternal sera at term tended to be higher (median: 469 pmol/L, range 61-980 pmol/L, P < 0.1) than at 6-11 weeks (286 pmol/L, 61-653 pmol/L) or in sera from nonpregnant women (306 pmol/L, 204-469 pmol/L). In umbilical cord sera, median CgA level was significantly higher (898 pmol/L, 102-2245 pmol/L, P < 0.05) than in term sera. Median serum level of PST-LI was significantly higher at term (38 pmol/L, 0-131 pmol/L) than at 6-11 weeks (9 pmol/L (0-85 pmol/L, P < 0.05), than in nonpregnant women (6 pmol/L, 0-52 pmol/L, P < 0.05), and in umbilical cord sera (12 pmol/L, 0-76 pmol/L, P < 0.05). In amniotic fluid, median CgA value was significantly higher at term (1163 pmol/L, 714-1673 pmol/L) than at 14-17 weeks (551 pmol/L, 82-980 pmol/L, P < 0.01), whereas median level of PST-LI was significantly higher at 14-17 weeks (32 pmol/L, 6-97 pmol/L) than at term (0 pmol/L, 0-15 pmol/L, P < 0.01). To our knowledge, this is the first report describing the presence of CgA and PST-LI in placenta and amniotic fluid and the occurrence CgA mRNA in placental tissue and in a placental cell line. The presence of CgA in placenta may indicate a physiological role in pregnancy.

Plasma pancreastatin-like immunoreactivity correlates with plasma norepinephrine levels in essential hypertension.

Pancreastatin (PST), a 49 amino acid peptide originally isolated from porcine pancreas, is derived from chromogranin A (Cg A), an acidic protein co-released with catecholamines from sympathetic nerve terminals and chromaffin cells. Extracellular processing of Cg A yields PST as well as other biological active peptides. Measurement of Cg A and PST-like immunoreactivity (PST-LI) has been used to investigate patients with pheochromocytoma and other neuroendocrine neoplasia. Some studies have found increased plasma norepinephrine (NE) levels in essential hypertension. We therefore measured venous plasma PST-LI and catecholamines in patients with essential hypertension. We employed a radioimmunoassay developed with commercially available reagents for measuring plasma PST-like immunoreactivity, and HPLC with electrochemical detection for measurement of plasma catecholamines. The correlation of PST-LI with epinephrine (E) was very weak. However, its correlation with NE was highly significant. Thus, venous plasma PST-LI immunoreactivity may reflect sympathetic nerve activity in essential hypertension.

Increased plasma pancreastatin-like immunoreactivity levels in non-obese patients with essential hypertension.

DESIGN: Pancreastatin, a novel peptide, is known to inhibit insulin secretion and to have a glycogenolytic effect, and is present in many endocrine and chromaffin cells. Both the plasma insulin levels and the adrenergic activity accompanying insulin resistance have been shown to be increased in hypertensive subjects. Our working hypothesis was that pancreastatin might play a role in these pathological phenomena. METHODS: We studied the plasma pancreastatin level in non-obese essential hypertensive patients in response to an intravenous glucose load. We further measured the responses to the glucose challenge of insulin, glucagon, catecholamines and free fatty acids, as well as other factors related to insulin resistance (i.e. lipoproteins and apolipoproteins). We separated the hypertensive patients into three groups according to their response to an oral glucose-tolerance test: normoinsulinaemic, hyperinsulinaemic and glucose-intolerant. Matched normotensive control subjects were also studied. RESULTS: Pancreastatin levels did not change in the control group after the glucose challenge. However, all hypertensive patients showed an increase in plasma pancreastatin levels after glucose loading. The normoinsulinaemic hypertensive patients also had elevated basal pancreastatin levels. The increase in pancreastatin levels was in the ranking: normoinsulinaemic > hyperinsulinaemic > glucose-intolerant. The pancreastatin: insulin ratio showed that the secretion of pancreastatin and insulin may be regulated differently. Basal free fatty acid and glucagon levels were found to be elevated both in the hyperinsulinaemic and in the glucose-intolerant group. Fasting triglycerides levels were increased in all of the hypertensive patients. Other risk factors for coronary artery disease were also found to be altered: elevated very low-density lipoprotein-cholesterol and decreased high-density lipoprotein-cholesterol, with ranking: normoinsulinaemic < hyperinsulinaemic < glucose-intolerant. CONCLUSIONS: These results show an increase in pancreastatin levels in hypertensive patients, suggesting that pancreastatin might play a role in the pathophysiology of essential hypertension.

Ontogeny and regional distribution of hormone-producing cells in the embryonic pancreas of Alligator mississippiensis.

The hormones of the endocrine pancreas are believed to play an important role in early development. The development of the pancreas and the appearance of hormone-producing cells during embryogenesis have been extensively studied in mammals and birds. Relatively little work has been done in other vertebrates, and there are no published studies regarding the order Crocodilia. Given the pivotal phylogenetic position of crocodilians, Alligator mississippiensis provides an interesting species in which to study the embryonic development of the endocrine pancreas. The aims of the present study were (1) to investigate the morphological development of the pancreas and (2) to determine the initial appearance and regional distribution of the pancreatic endocrine cells in the embryonic alligator. At each stage of development serial sections of pancreatic tissue were stained with hematoxylin and eosin to aid in morphological description. Using immunocytochemistry sections were stained to detect the presence of insulin, glucagon, somatostatin, and pancreatic polypeptide. The dorsal pancreatic bud was first observed at stage 8, coincident with the appearance of insulin-containing and glucagon-containing cells. Somatostatin-containing cells were first detected at stage 10. At stage 13 the ventral pancreatic bud was first observed. At stage 14 the dorsal and ventral pancreatic buds fused and insulin, glucagon, and somatostatin were found throughout the pancreas. Not until stage 17 was pancreatic polypeptide first detected. Unlike the other hormones, pancreatic polypeptide was rare or absent in the dorsal region of the pancreas. In later stages of development, somatostatin-containing cells were the most abundant and constituted 35-40% of all hormone-containing cells. The sequence of appearance of insulin and glucagon found in the alligator is the same as that found in mammals and birds.

Pancreastatin-like immunoreactivity in the pancreas of newborn rats.

Pancreastatin (PST), a novel COOH-terminally alpha-amidated peptide is a part of Chromogranin A molecule. Precursor processing implies also the final amidation step dependent on peptidylglycine alpha-amidating monooxygenase (PAM). High activity of PAM as well as Thyroliberin (TRH, another alpha-amidated peptide) concentration and biosynthesis were reported to be very high in neonatal rat pancreas. We followed the concentration of PST-like immunoreactivity in rat pancreas during ontogenesis. High perinatal PST concentration, resembling that of previously reported for PAM activity and TRH concentration was found. These findings suggest that perinatal PAM activation may affect a broader spectrum of pancreatic peptides.

Unique change of pancreastatin-like immunoreactivity in cerebrospinal fluid by aging.

Using a specific antiserum for the C-terminal glycine amide region of human pancreastatin (PST), pancreastatin-like immunoreactivity (PST-LI) was measured in cerebrospinal fluid (CSF) from 447 subjects (368 +/- 10.8 pmol/l, mean +/- S.E.M.) free from endocrine diseases. The CSF contents of PST-LI showed a mountain-shape type change which peaked at 40 years of age. The highest concentration was found in the group of ages 40-49 years old (412 +/- 22.9 pmol/l) and the lowest concentration was found in the group of ages 80-89 years old (293.2 +/- 45.2 pmol/l) among various age groups. Gel chromatographic examination revealed the presence of two major forms (MW 13,500 and 5,400) of PST-LI in CSF. Because of the character of this antibody, the large molecular form is possibly an N-terminally elongated PST and the other may be PST-52. This may be the first report on the unique age-related change of PST concentration in CSF.

Immunoassays for measurement of chromogranin A and pancreastatin-like immunoreactivity in humans: correspondence in patients with neuroendocrine neoplasia.

Chromogranin A (CgA) is a useful marker of neuroendocrine tumors in humans. Here we describe and compare two immunoassay methods for determination of CgA, a radioimmunoassay (RIA) and an enzyme linked immunoassay (ELISA). The detection limit of the ELISA was lower than that of the RIA method (2 ng/ml versus 10 ng/ml, respectively), though the CgA RIA method covered a wider range than the CgA ELISA (10-920 ng/ml versus 2-500 ng/ml, respectively). There was no cross-reactivity with synthetic human and porcine pancreastatin (PST) in the two assays. There was a significant positive correlation between levels of CgA in sera from patients with carcinoid disease, measured by the two methods (r = 0.9, p < 0.0001), and the values were in the same range. Similarly, serum CgA levels in normal controls were also in the same range when assayed by the two methods. A commercially available porcine PST RIA method was evaluated, especially with respect to the influence of Sep-Pak extraction of serum on the levels of pancreastatin-like immunoreactivity (PST-LI). Ten sera from carcinoid patients were treated with Sep-Pak extraction, and levels of PST-LI were determined in non-extracted and extracted sera. There was a significant positive correlation between the concentrations of PST-LI measured in extracted and non-extracted carcinoid sera (r = 0.9, p < 0.002), and the levels were in the same range. There was also a significant positive correlation between levels of CgA and PST-LI in 49 carcinoid sera (r = 0.8, p < 0.0001).(ABSTRACT TRUNCATED AT 250 WORDS)

A phylogenetic survey of pancreastatin and chromogranin immunoreactivity in chromaffin (TH-, DBH-, and PNMT-immunoreactive) cells of the adrenal organ of vertebrates.

Region-specific antisera raised against different amino acid sequences of pancreastatin (Pst) (Pst-1-6, Pst-1-17, Pst-14-49 and Pst-33-49) and two antisera towards chromogranin (Cg) A and CgA/B were applied in immunofluorescence to examine the occurrence and distribution of Pst-immunoreactive (-IR) and Cg-IR cells in adrenal organs of several mammals, birds, reptiles, amphibia, and bony fish. The catecholamine-containing cells were identified using antisera against enzymes of catecholamine synthesis (tyrosine-hydroxylase, dopamine-beta-hydroxylase, and phenylethanolamine-N-methyl-transferase). No animal showed any Pst-IR or Cg-IR cells in the adrenal cortex or in its homolog, the interrenal. All antisera reacted with chromaffin cells in porcine adrenal medulla. Both adrenaline (A)- and noradrenaline (NA)-containing cells displayed Pst- and Cg-immunoreactivity. Pst- and CgA-immunoreactivities were observed in coexistence using double immunofluorescence. However, strongly reacting Pst-IR cells showed only low CgA immunoreactivity and vice versa. This inverse relationship between Pst- and CgA-immunoreactivities might reflect different levels of processing of the likely Pst-precursor CgA. In all nonmammalian vertebrates studied, Pst- and Cg-immunoreactivities were also found in both A- and NA-containing adrenal cells. However, the chromaffin cells reacted only with the antisera Pst-1-6, Pst-1-17, Pst-33-49, and CgAB. The adrenal chromaffin cells of nonmammalian vertebrates appear to contain Pst-/Cg-like peptides akin to those of the enteroendocrine cells but different from those of their endocrine pancreas. Since no immunoreactions were obtained with antiserum CgA, nonmammalian Pst may be derived from a precursor different from mammalian CgA.

Chromogranin A and pancreastatin-like immunoreactivity in serum of gastrinoma patients.

Gastrin and pancreastatin-like immunoreactivity were determined by radioimmunoassay methods and chromogranin A was determined by enzyme-linked immunoassay in sera from 18 patients with gastrinomas (Zollinger-Ellison syndrome) and in 20 age and sex matched controls. Gastrin serum levels in the gastrinoma patients were in the range 26-80,000 pmol/l, and in the controls 5-31 pmol/l. Chromogranin A serum levels in the gastrinoma group were in the range 6-2,700 ng/ml (mean +/- SEM: 400 +/- 147 ng/ml). The mean value of chromogranin A was significantly higher than in the control group (8 +/- 2 ng/ml, p = 0.008). The serum levels of pancreastatin-like immunoreactivity in the gastrinoma patients were in the range 23-1,994 pg/ml (597 +/- 123 pg/ml). The mean value of pancreastatin-like immunoreactivity in the gastrinoma group was significantly higher than in the control group (104 +/- 25 pg/ml, p = 0.0002). The levels of chromogranin A and pancreastatin-like immunoreactivity were significantly higher in patients with verified metastatic disease (p = 0.04, p = 0.01 respectively). There was a significantly positive correlation between levels of gastrin and pancreastatin-like immunoreactivity (r = 0.7, p = 0.002), while no correlation was found between gastrin and chromogranin A levels or between levels of chromogranin A and pancreastatin-like immunoreactivity. The study demonstrates an elevation of both chromogranin A and pancreastatin-like immunoreactivity in serum of gastrinoma patients. The lack of correlation between gastrin and chromogranin A, however, gives an indication that the gastrinoma cells are not the main source of serum chromogranin A elevation.

Immunocytochemical localisation of pancreastatin and chromogranin A in porcine neuroendocrine tissues.

Pancreastatin is a 49 amino acid peptide with a C-terminal glycine amide originally isolated from porcine pancreas. In the present study the cellular localisation of pancreastatin in porcine neuroendocrine tissue was examined immunocytochemically using an antiserum raised against porcine pancreastatin (33-49) that does not cross-react with porcine chromogranin A. In order to study the possible precursor-product relationship between chromogranin A and pancreastatin the cellular localisation of both peptides was examined in peripheral tissues using simultaneous double immunostaining. The pancreastatin antiserum immunostained cells and nerve fibers throughout the neuroendocrine system. In most of the examined tissues we found colocalisation of pancreastatin and chromogranin A immunostaining. These results support the precursor-product concept for chromogranin A and pancreastatin. However, in the gastrointestinal tract and the adenohypophysis a minor population of the endocrine cells exhibited immunostaining with only one of the two antibodies. This discrepancy between immunostaining with pancreastatin antiserum and monoclonal chromogranin A antibody could be due to absence of, or extensive, processing of chromogranin A in certain cell populations.

Amyloid protein in somatostatinoma differs from human islet amyloid polypeptide.

Amyloid deposits in somatostatinomas are rare observations. To examine the characteristics of this amyloid, we compared amyloid deposits in a somatostatinoma to those found in pancreatic tissue in patients with Type II diabetes mellitus and in insulinomas, using immunohistochemical techniques and specific antibodies to islet amyloid polypeptide or other pancreatic hormones, as well as electron-microscopy. Antibodies to islet amyloid polypeptide regions 8-17 or 25-37 were confirmed to be specific. Amyloid deposits in patients with Type II diabetes mellitus and in insulinomas, but not those in the somatostatinoma strongly reacted with these antibodies, or to an antibody to amyloid P component. Amyloid deposits in the somatostatinoma were not reactive with antibodies to somatostatin or to other pancreatic hormones. Electron-microscopic examinations revealed that amyloid fibrils in the somatostatinoma were thinner and more randomly distributed than were those in islets from patients with Type II diabetes mellitus. As amyloid in somatostatinomas is unlike that consisting of islet amyloid polypeptide or other mature pancreatic hormones, it may be a novel type of local amyloid in pancreatic islets.