Pancreastatin Immunoreactivity Research Articles

Pancreastatin plasma levels in patients with primary hyperparathyroidism.

Pancreastatin, a C-terminally amidated peptide derived from chromogranin A, is known to inhibit insulin secretion, pancreatic enzyme release, and gastric acid secretion. It also inhibits parathyroid hormone (PTH) secretion in animals. The physiologic and clinical relevance of pancreastatin in humans, however, is not known. Because pancreastatin has been found in parathyroid adenomas, we investigated the plasma levels in patients with primary hyperparathyroidism (pHPT). Thirteen patients operated on for solitary parathyroid adenoma were investigated. Plasma levels of pancreastatin and serum levels of ionized calcium and intact PTH were measured before and 6 weeks after operation. In 10 patients the levels were also monitored before and 60 minutes after adenoma excision. The adenomas were investigated for pancreastatin immunoreactivity by immunocytochemistry. The median weight of the excised parathyroid adenoma was 0.64 g (range 0.07-2.00 g). Cells displaying pancreastatin immunoreactivity were present in all adenomas examined and varied in number and immunostaining intensity among and within the adenomas. Intraoperatively, after adenoma excision the levels of PTH and pancreastatin declined (p < 0.01), whereas the levels of ionized calcium did not change (p = 0.96). At the 6-week follow-up the levels of ionized calcium and PTH had decreased compared to the preoperative levels (p < 0.01), and all patients were normocalcemic. In contrast, the pancreastatin levels were not changed (14.5 +/- 6.1 pmol/L preoperatively vs. 12.8 +/- 11.2 pmol/L 6 weeks postoperatively; p = 0.12). In patients with pHPT, pancreastatin is likely to be produced by the parathyroid adenoma. The changes in pancreastatin levels immediately after surgery warrant further investigation.

Prohormone convertase-1 is essential for conversion of chromogranin A to pancreastatin

The purpose of this study was to test the hypothesis that the endoprotease, prohormone convertase-1 (PC-1), is involved in the processing of the precursor protein chromogranin A (CGA) to a smaller peptide called pancreastatin (PST). A human pancreatic carcinoid cell line (BON) that expresses PC-1, CGA and PST was stably transfected with antisense PC-1 mRNA. BON cells expressing antisense PC-1 mRNA showed nearly complete abolishment of PC-1 protein (∼95% reduction) and an 80% reduction in cell content of PST immunoreactivity (PST-IR) as assessed by high-performance liquid chromatography in combination with measurement of PST-IR. These findings indicate that PC-1 is essential for processing CGA to PST.

Pancreastatin immunoreactivity in favourable childhood neuroblastoma and ganglioneuroma

Neuroblastoma and its benign counterpart, ganglioneuroma, are tumours of the sympathetic nervous system, and known to produce and release various regulatory peptides. In this study, pancreastatin, a 52 amino acid regulatory peptide derived from chromogranin A, was analysed in plasma and tumour tissue from 15 children with neuroblastoma and one with ganglioneuroma. Detectable pancreastatin immunoreactivity (> 1.9 pmol/l) was found in plasma in 13 of 15 children with highest concentrations in samples from children with favourable outcome (P < 0.05). In tumour tissue, non-metastatic tumours showed higher concentrations of pancreastatin immunoreactivity (P < 0.05). However, the highest concentrations were detected in tumours from children with favourable prognosis, regardless of clinical stage at presentation (P < 0.01). Serial plasma samples from one child with neuroblastoma and one with ganglioneuroma were investigated and showed significant systemic release of pancreastatin immunoreactivity during surgical manipulation of tumours with high pancreastatin concentrations. It is concluded that pancreastatin immunoreactivity may be detected in plasma samples and tumour extracts from children with neuroblastoma and ganglioneuroma. Systemic release during surgery implied tumour origin of elevated plasma pancreastatin. Furthermore, higher pancreastatin concentrations correlate with tumour differentiation, localised clinical stage and a favourable outcome for children with these tumours. It is suggested that pancreastatin in plasma and tumour tissue may be utilised as a marker indicating favourable tumour behaviour.

The post-translational processing of chromogranin A in the pancreatic islet: involvement of the eukaryote subtilisin PC2

The post-translational processing of chromogranin A (CGA) and the nature of the enzyme(s) involved were investigated in rat pancreatic islet and insulinoma tissue. Pulse-chase radiolabelling experiments using sequence-specific antisera showed that the 98 kDa (determined by SDS/PAGE) precursor was processed to an N-terminal 21 kDa peptide, a C-terminal 14 kDa peptide and a 45 kDa centrally located peptide with a rapid time course (t1/2 approx. 30 min) after an initial delay of 30-60 min. The 45 kDa peptide was, in turn, converted partially into a 5 kDa peptide with pancreastatin immunoreactivity and a 3 kDa peptide with WE-14 immunoreactivity over a longer time period. Incubation of bovine CGA with rat insulinoma secretory-granule lysate produced peptides of 18, 16 and 40 kDa via intermediates of 65 and 55 kDa. N-terminal sequence analysis indicated that cleavage occurred at the conserved paired basic sites Lys114-Arg115 and Lys330-Arg331, suggesting that cleavage of the equivalent sites (Lys129-Arg130 and Lys357-Arg358) in the rat molecule produced the initial post-translational products observed in intact pancreatic beta-cells. The enzyme activity responsible for the cleavage of bovine CGA co-chromatographed on DEAE-cellulose with the type-2 proinsulin endopeptidase and with PC2 immunoreactivity. The type-1 enzyme (PC1/3) appeared inactive towards CGA. The requirement for Ca2+ ions and an acidic pH for conversion was consistent with the involvement of a member of the eukaryote subtilisin family, and the composition of the released peptides in pulse-chase and secretion studies suggested that conversion occurred in the secretory-granule compartment. The overall catalytic rate as well as the relative susceptibilities of the Lys114-Arg115 and Lys330-Arg331 sites to cleavage were affected by pH, suggesting that the ionic environment of the processing compartment may play a role in the differential processing of CGA which is evident in various neuroendocrine cells.

Secretion of pancreastatins from isolated, perfused, porcine adrenal glands

Pancreastatin is a 49 amino acid peptide with a C- terminal glycine amide originally isolated from porcine pancreas. There are strong indications that pancreastatin is derived from chromogranin A, since the amino acid sequence 240–288 in porcine chromogranin A contains pancreastatin flanked by typical signals for proteolytic processing. Several molecular forms of immunoreactive pancreastatin have been reported to be present in porcine adrenal medulla, but no information on the secretion of the peptides is available. We studied stimuli for the release of immunoreactive pancreastatin from adrenal glands as well as the molecular nature of the released immunoreactivity using isolated, perfused, porcine adrenal glands with intact splanchnic nerve supply and a radioimmunoassay specific for the C- terminal glycine amide of porcine pancreastatin in combination with chromatography. Stimulation of the splanchnic nerves greatly enhanced the release of immunoreactive pancreastatin by a mechanism that seems to involve cholinergic nicotinic transmission. The pancreastatin immunoreactivity was due to large amounts of a N- terminally extended pancreastatin form, possibly corresponding to the chromogranin A(1–288) fragment and small amounts of pancreastatin and a C- terminal pancreastatin fragment. Adrenal extracts also contained unprocessed chromogranin A. We conclude that in the porcine adrenals at least 25% of chromogranin A is processed to smaller molecular forms with the pancreastatin sequence forming their C- terminus . These forms appear to be released in parallel with the catecholamines.

Secretion of pancreastatins from the porcine digestive tract.

Pancreastatin, a 49-amino acid peptide with a COOH-terminal glycine amide, was originally isolated from porcine pancreas, but pancreastatin immunoreactivity has been found in several neuroendocrine tissues. There are strong indications that pancreastatin is derived from chromogranin A, since the amino acid sequence 240-288 in porcine chromogranin A corresponds to pancreastatin flanked by typical signals for proteolytic processing. We have studied the effect of electric stimulation of the nervous supply to perfused porcine pancreas, antrum, nonantral stomach, and small intestine on the release of immunoreactive pancreastatin, and we characterized the molecular nature of the secreted immunoreactivity by using a radioimmunoassay specific for the COOH-terminal glycine amide of porcine pancreastatin in combination with chromatography. In all tissues nerve stimulation significantly increased the release of immunoreactive pancreastatin. The secreted immunoreactive pancreastatin was heterogeneous, consisting of pancreastatin itself, a COOH-terminal pancreastatin fragment, and NH2-terminally extended pancreastatin forms. Pancreastatin predominated in the perfusate from pancreas and antrum, whereas mainly NH2-terminally extended molecular forms were secreted from the antrectomized stomach and small intestine. The different molecular forms of pancreastatin were secreted from the perfused organs in the same molar ratio as they occur in extracts of the corresponding tissues. Thus, pancreastatin and other chromogranin A-derived peptides in organ-specific proportions regularly accompany the secretion of the peptide hormones from the gastrointestinal tissues on appropriate stimulation.

Pancreastatin immunoreactivity in the circulation of patients with carcinoid tumours

Pancreastatin immunoreactivity in the circulation of patients with carcinoid tumours

Novel peptide pancreastatin: its occurrence and codistribution with chromogranin A in the central nervous system of the pig.

The distribution of pancreastatin immunoreactivity was investigated in porcine brain, spinal cord, dorsal root ganglia, and pituitary. In the brain, immunoreactive cell bodies were present in many areas including the cortex, basal ganglia, hippocampus, thalamus, hypothalamus, mesencephalic reticular formation, cerebellum, and medulla oblongata. Immunoreactive fibres were most abundant in the globus pallidus, stria terminalis, entopeduncular nucleus, hippocampus, and in the substantia nigra. In the spinal cord, immunoreactive cells were found in laminae IV-IX. Immunoreactive fibres were concentrated in the dorsal horn. Pancreastatin immunoreactivity was localised to fibres and small cells (5-10% of the total) in the dorsal root ganglia. In the posterior pituitary, many immunoreactive fibres were present and in the anterior lobe subsets of gonadotrophs and thyrotrophs were pancreastatin-immunoreactive. The localisation of pancreastatin showed a parallel distribution with chromogranin A. Coexistence of pancreastatin with calcitonin gene-related peptide (CGRP) immunoreactivity in cell bodies in the spinal cord, including motoneurones, and with CGRP or galanin immunoreactivities in dorsal root ganglion cells was also noted. The differential pattern of pancreastatin immunostaining was reflected in the extractable levels of peptide with highest concentrations in the cortex (55.8 +/- 6.0 pmol/g wet weight, mean +/- S.E.M.), thalamus (60.0 +/- 5.0 pmol/g), hypothalamus (54.4 +/- 6.5 pmol/g), and anterior pituitary (2,714 +/- 380 pmol/g). Characterisation of pancreastatin immunoreactivity in the hypothalamus and pituitary by gel permeation and high-pressure liquid chromatography revealed multiple molecular forms, one of which was indistinguishable from natural porcine pancreastatin. The widespread distribution of pancreastatin immunoreactivity suggests this peptide may play a part in several neuroendocrine, autonomic, somatic, and sensory functions, and its colocalisation with chromogranin A is consistent with a precursor-product relationship.

Pancreastatin-like immunoreactivity and insulin are released in parallel from the perfused porcine pancreas.

Pancreastatin, a peptide isolated from the porcine pancreas, suppresses insulin release from pancreatic islets of the rat. Pancreastatin immunoreactivity has been localized to islet B and D cells in the porcine pancreas. We have developed a RIA for this peptide, using rabbit anti-porcine pancreastatin antibodies and 125I-Tyr-pancreastatin. Isolated pig pancreata were perfused with a nonrecirculating bicarbonate buffer solution containing 4% Dextran and 0.1% Albumin. Glucose (11 mmol/liter) induced a biphasic release of pancreastatin-like immunoreactivity (PLI). Electrical stimulation of the vagus nerves (8 Hz), as well as perfusion with acetyl choline (10(-6) mol/liter) in the presence of 5.5 mmol/liter glucose, also evoked prompt PLI responses. Furthermore, truncated GLP-1 (proglucagon 78-107; 10(-9) mol/liter) induced PLI release. All tested stimuli also elicited insulin secretion. To investigate whether the PLI measured could be ascribed to secretion of the low molecular weight pancreastatin (Mr 5,100) or to a possible precursor such as chromogranin A (Mr approximately 75,000), perfusates containing PLI were subjected to gel filtration on an Ultropac G3000SW column. All of the PLI was recovered at the elution position of the pancreastatin marker. In conclusion, PLI and insulin are released in parallel from the perfused porcine pancreas, exposed to stimuli known to affect insulin release.

Pancreastatin distribution and plasma levels in the pig.

Pancreastatin is a peptide isolated from porcine pancreas which has insulin-suppressive actions in vitro and sequence homology with chromogranin A. Using radioimmunoassay and immunocytochemistry we investigated whether pancreastatin has a more widespread distribution and a possible endocrine role in the pig. Pancreastatin immunoreactivity was found in plasma, adrenal gland, pancreas, anterior pituitary and throughout the gastrointestinal tract. The immunoreactivity was colocalized with chromogranin immunoreactivity in endocrine cells and ultrastructurally (in the pancreas) to storage granules. Characterization of pancreastatin-like immunoreactivity, using gel permeation and high performance liquid chromatography, separated 3 different pancreastatin-like immunoreactive forms: one molecular form, indistinguishable from synthetic pancreastatin 1-49, was predominant in pancreas and thyroid and released into the circulation postprandially. However, a high dose (greater than 1 nmol/l) infusion of pancreastatin 33-49 (the biologically active moiety in vitro) into conscious pigs had no effect on either basal or glucose-stimulated insulin secretion.

Differential colocalisation of porcine pancreastatin immunoreactivity in the head and tall regions of the rat pancreas

Differential colocalisation of porcine pancreastatin immunoreactivity in the head and tall regions of the rat pancreas

Localization of pancreastatin immunoreactivity in porcine endocrine cells.

Pancreastatin is a peptide isolated from the porcine pancreas and shown to inhibit insulin release. We have studied the immunocytochemical distribution of pancreastatin in three porcine endocrine tissues: pancreas, gut, and adenohypophysis. Pancreastatin-specific immunoreactivity was found in all three locations and distributed to numerous cells. In the pancreas, we performed the alternate labeling of consecutive thick (immunofluorescence) or thin (protein A-gold) sections and we observed that pancreastatin colocalizes to secretory granules of insulin and somatostatin-containing cells. The relationship of pancreastatin to chromogranin A is discussed.

C-terminal pancreastatin immunoreactivity in the pancreas of several mammals

C-terminal pancreastatin immunoreactivity in the pancreas of several mammals