Large variations in the proteolytic formation of a chromogranin A-derived peptide (GE-25) in neuroendocrine tissues

We have established a radioimmunoassay for GE-25, a peptide present in the C-terminal end of the primary amino acid sequence of chromogranin A where it is flanked by typical proteolytic cleavage sites. Gel-filtration HPLC was used to characterize the molecular sizes of the immunoreactive molecules. The antiserum recognized not only the free peptide but also larger precursors including the proprotein chromogranin A. The tissues with the highest levels of GE-25 immunoreactivity were in decreasing order: the adrenal medulla, the three lobes of the pituitary gland, intestinal mucosa, pancreas and various brain regions. In adrenal medulla and parathyroid gland most of the immunoreactivity was found to be present as intact chromogranin A and some intermediate-sized peptides, without significant amounts of the free peptide. In anterior pituitary, and even more so in intestine, a shift to smaller peptides was seen. In the posterior and intermediate pituitary and in pancreas the predominant immunoreactive material was apparently represented by the free peptide GE-25. In reverse-phase chromatography this peptide eluted exactly like the synthetic standard, which allows a tentative identification as GE-25. In brain tissue the processing of chromogranin A was intermediate, with significant amounts of immunoreactivity corresponding to GE-25 as well as precursor proteins being present. We suggest that in those organs (endocrine pancreas, intermediate and posterior pituitary) where the major hormones are proteolytically processed there is also a concomitant proteolysis of further susceptible peptides. Since GE-25 is apparently formed in vivo and is well conserved between species it seems a good candidate for having specific physiological functions.

Sustained dopamine release induced by secretoneurin in the striatum of the rat: a microdialysis study

Secretoneurin (SN) is a neuropeptide derived from secretogranin II that is found in brain and endocrine tissues. The aim of the present study was to determine the influence of this novel peptide on dopamine (DA) release from rat striatum using the microdialysis technique. Rat SN (1-30 mumol/L added to the dialysis buffer) enhanced DA outflow of awake rats in a concentration-dependent way without marked effects on the outflow of 3,4-dihydroxyphenylacetic acid or homovanillic acid. The increase in extracellular DA content caused by the peptide was observed throughout the entire period of administration (up to 4 h). Human SN and its 15-amino-acid C-terminal sequence also increased DA outflow, but the effects were smaller than those of rat SN. Two other peptides derived from secretogranin II were without effect on DA efflux. These results establish that SN has a pronounced effect on DA release under in vivo conditions.

Secretoneurin: a new peptide in the human enteric nervous system

Secretoneurin is a functional neuropeptide derived from secretogranin II (chromogranin C). This proprotein is processed to varying degrees in neuroendocrine tissues. In the present study we established by gel filtration high performance liquid chromatography that in human intestinal wall and mucosa an antiserum against secretoneurin detects as the major immunoreactive moiety the free peptide secretoneurin. In the mucosa some larger immunoreactive peptides were also present, however, a significant amount of the intact proprotein secretogranin II could not be detected. By immunohistochemistry we studied the distribution of secretoneurin within the gut. Antibodies to protein gene product 9.5 and chromogranin A were used to identify all neurons and endocrine cells, respectively, whilst those to the peptides substance P, CGRP and somatostatin were used for the further characterization of individual secretoneurin-positive structures. Secretoneurin immunoreactivity was found in nerve fibres in all layers of the gut wall. In both myenteric and submucous plexuses, nerve fibres and the majority of ganglion cells were secretoneurin-immunoreactive. In the mucosa, some secretoneurin-positive nerve processes ran parallel to the basal membrane of epithelial cells, occasionally invading the epithelial layer. Secretoneurin immunoreactivity was found in endocrine cells, mostly D cells, in the following regions in descending order of density: stomach/duodenum; rectum; colon; ileum. Thus, secretoneurin is a new major peptide within the human enteric neuroendocrine system. Its presence in abundant myenteric ganglion cells may imply a role in the modulation of gastrointestinal motility. The chemotactic properties of secretoneurin and its possible localization in sensory fibres suggest that this peptide may be involved in the genesis of intestinal inflammation.

Secretoneurin-immunoreactivity in nerve terminals apposing identified preganglionic sympathetic neurons in the rat: colocalization with substance P and enkephalin

Preganglionic sympathetic neurons projecting to the superior cervical ganglion are innervated by nerve fibers containing classical neurotransmitters as well as neuropeptides. In this study we examined the possible participation of a novel peptide, secretoneurin (a cleavage product of secretogranin II), in regulation of sympathetic outflow to head and neck by using a retrograde labelling-technique combined with immunohistochemistry. In addition, the coexistence of secretoneurin with substance P and leu-enkephalin, peptides known to innervate preganglionic neurons, was investigated. The majority of retrogradely labeled neurons were localized in the nucleus intermediolateralis of spinal cord segments T1-T3 (maximum at T2). Nearly all of Fast Blue positive neuronal perikarya were apposed by nerve fibers and terminals exhibiting immunoreactivity to secretoneurin. The main secretoneurin-immunoreactive form found in the upper thoracic segments corresponded to the free peptide secretoneurin as revealed by chromatography and radioimmunoassay. More than half of labeled neurons were surrounded by nerve endings containing in addition substance P or leu-enkephalin which were also, however, less frequently colocalized. Our results suggest that secretoneurin influences the activity of preganglionic sympathetic neurons projecting to the superior cervical ganglion. Regarding their frequent colocalization with substance P and leu-enkephalin, functional interactions of these peptides on preganglionic sympathetic nerve activity have to be considered.

Calcitonin and calcitonin gene-related peptide mRNA detection in a population of hyperplastic parathyroid cells also expressing chromogranin B

BACKGROUND

In contrast to chromogranin A, chromogranin B is found only in small amounts in parathyroid tissue. We have recently shown that hyperplastic parathyroid glands occasionally show a pronounced focal chromogranin B expression. The aim of the present study was to further investigate the properties of these chromogranin B-positive cells by means of immunohistochemistry and in situ hybridization.

EXPERIMENTAL DESIGN

Routinely processed tissues from 22 normal, 86 hyperplastic, and 36 neoplastic parathyroid glands were immunohistochemically investigated with Ab against parathyroid hormone (PTH), chromogranin A and B, calcitonin, and calcitonin gene-related peptide (CGRP). Additionally, six hyperplastic glands with focal chromogranin immunoreactivity as well as chromogranin B-negative normal, hyperplastic, and neoplastic (two cases each) glands were used for in situ hybridization studies for the demonstration of calcitonin and CGRP mRNA.

RESULTS

All normal, hyperplastic, and neoplastic parathyroids were immunohistochemically PTH- and chromogranin A-positive. Twelve of 86 hyperplastic glands showed a focal chromogranin B immunoreactivity; in 10 out of these 12 cases, calcitonin could be colocalized with chromogranin B, chromogranin A, and PTH. CGRP was found in a fraction of calcitonin-positive cells in four cases. In hyperplastic glands, calcitonin mRNA was detected in areas with immunohistochemical calcitonin and chromogranin B positivity. CGRP mRNA was demonstrated only in a few cells.

CONCLUSIONS

The results from this study demonstrate that calcitonin and CGRP may be synthesized and stored in PTH-producing hyperplastic parathyroid cells. The calcitonin-positive cells also strongly express chromogranin B, which is immunohistochemically not detectable in normal parathyroid cells. The functional significance of these findings remains to be elucidated.

Immunohistochemical detection of secretoneurin, a novel neuropeptide endoproteolytically processed from secretogranin II, in normal human endocrine and neuronal tissues

An antiserum raised against a synthetic peptide derived from the primary amino sequence of rat secretogranin II (chromogranin C) was used for immunological (quantitative radioimmunoassay analysis) and immunohistochemical studies of normal human endocrine and nervous tissues. This antibody recognized a novel and biologically active neuropeptide which was coined as secretoneurin. In endocrine tissues, secretoneurin was mainly co-localized with chromogranin A and B with some exceptions (e.g., parathyroid gland). Secretoneurin was demonstrated immunohistochemically in the adrenal medulla, thyroid C cells, TSH- and FSH/LH-producing cells of the anterior pituitary, A and B cells of pancreatic islets, in endocrine cells of the gastrointestinal tract and the bronchial mucosa, and the prostate. Immunoreactivity determined by radioimmunoassay analysis revealed high secretoneurin levels in the anterior and posterior pituitary and lower levels in pancreatic and thyroid tissue. A strong secretoneurin immunoreactivity was also found in ganglion cells of the submucosal and myenteric plexus of the gastrointestinal tract, and in ganglionic cells of dorsal root ganglia, peripheral nerves, and ganglion cells of the adrenal medulla. Thus, secretoneurin may serve as a useful marker of gangliocytic/neuronal differentiation.

Immunohistochemical distribution of chromogranins A and B and secretogranin II in neuroendocrine tumours of the gastrointestinal tract

The aim of the present study was to investigate immunohistochemically the distribution of chromogranin A, chromogranin B, and secretogranin II in a series of 152 neuroendocrine tumours of the gastrointestinal tract. Tumour tissues from 25 argyrophil gastric carcinoids, 18 gastrin and 5 somatostatin-producing tumours, 4 'gangliocytic paragangliomas', 49 classical argentaffin and 2 L cell appendiceal carcinoids, 27 classical ileal carcinoids, 17 rectal carcinoids, and 5 poorly differentiated neuroendocrine tumours of the stomach and rectum were immunostained with antibodies against chromogranin A, chromogranin B, and secretogranin II. Chromogranin A was the major granin expressed in gastric carcinoids and in serotonin-producing carcinoids of the appendix and the ileum. In contrast, strong chromogranin B and secretogranin II immunoreactivity was found in rectal carcinoids, in which chromogranin A was rarely expressed. Since chromogranin A is a widely used marker for neuroendocrine differentiation, it is of diagnostic importance that some gastrin-producing tumours, 'gangliocytic paragangliomas', poorly differentiated neuroendocrine carcinomas, and appendiceal L cell carcinoids completely lacked chromogranin A positivity. It is concluded that the various neuroendocrine tumours of the gastrointestinal tract show distinctly different patterns of granin expression, probably reflecting their histogenetical origin.

Secretogranin II: molecular properties, regulation of biosynthesis and processing to the neuropeptide secretoneurin

Secretogranin II is an acidic secretory protein in large dense core vesicles of endocrine, neuroendocrine and neuronal tissues. It comprises, together with chromogranins A and B, the class of proteins collectively called chromogranins. In this review the physico-chemical properties, genomic organization, tissue distribution, synthesis regulation, ontogeny and physiological function of this protein are discussed. Secretogranin II gained interest recently for mainly three reasons: (1) secretogranin II is an excellent marker for the regulated secretory pathway due to its simple and specific metabolic labeling by inorganic sulfate; (2) secretogranin II occurs in a variety of neoplasms arising from endocrine and neuroendocrine cells and was shown to be a useful histological tumor marker for these cells; (3) secretogranin II is the precursor of the recently discovered neuropeptide secretoneurin which induces dopamine release in the striatum of the rat brain.

Secretoneurin in bronchopulmonary carcinoids--immunohistochemical comparison with chromogranins A and B and secretogranin II

Ninety-nine classical and 11 atypical bronchopulmonary carcinoids were investigated immunohistochemically with an antibody against secretoneurin, a peptide proteolytically processed from secretogranin II (chromogranin C), as well as antibodies against chromogranin A and B and secretogranin II. Secretoneurin was immunolocalized in 86 tumours (78 classical and eight atypical carcinoids); secretogranin II was found in the same tumours in a similar distribution, whereas chromogranin A was present in all 100 and chromogranin B in 106 tumours investigated. Bronchopulmonary carcinoids are usually not associated with clinically or biochemically distinct syndromes. Although we found bronchial carcinoids with different immunohistochemical chromogranins/secretogranin patterns, no correlation with the biological behaviour of these tumours could be demonstrated.

Processing of secretogranin II by prohormone convertases: importance of PC1 in generation of secretoneurin

Secretoneurin is a recently characterized neuropeptide present in the primary amino acid sequence of secretogranin II. We investigated the proteolytic processing of secretogranin II by prohormone convertases in vivo in a cellular system using the vaccinia virus system. Both PC1 and PC2 can cleave the secretogranin II precursor at sites of pairs of basic amino acids to yield intermediate-sized fragments. Other convertases like PACE4, PC5 and furin were not active. For the formation of the free neuropeptide secretoneurin a different pattern was found. Only PC1 but none of the other convertases tested including PC2 were capable of generating secretoneurin. Our results demonstrate that the prohormone convertases PC1 and PC2 are involved in proteolytic processing of secretogranin II. The neuropeptide secretoneurin can only be generated by PC1 suggesting tissue-specific processing of secretogranin II in neurons expressing different subsets of the prohormone convertases.

Evidence for a high density of secretoneurin-like immunoreactivity in the extended amygdala of the rat

Secretoneurin is a novel 33-amino-acid neuropeptide produced by endoproteolytic processing from secretogranin II, which is a member of the chromogranin/secretogranin family. In this immunocytochemical study, we compared the distribution pattern of secretoneurin immunoreactivity with that of tyrosine hydroxylase, calbindin, substance P, and Leu-enkephalin in adjacent sections of rat forebrain. Secretoneurin appeared mainly in varicosities and fibers. Only a few cell bodies were stained. In the nucleus accumbens, a partial overlap of secretoneurin-immunoreactive patches with enkephalin-immunopositive areas was found. Secretoneurin displayed low to moderate levels of immunoreaction in calbindin-rich as well as in calbindin-immunonegative areas of the caudate-putamen. In the globus pallidus, entopeduncular nucleus, and substantia nigra, secretoneurin immunoreactivity was oriented ventromedially preferentially in woolly fibers. The dense immunostaining in the medial nucleus accumbens was directly continuous with dense secretoneurin immunoreactivity in the bed nucleus of the stria terminalis. Two strongly secretoneurin-immunopositive bands, one in the sublenticular portion and a smaller one along the posterior limb of the anterior commissure, interconnected the highly secretoneurin-immunopositive centromedial amygdala with the bed nucleus of the stria terminalis. Thus, the distribution pattern of secretoneurin immunoreactivity provides a marker of the extended amygdala that forms a continuum between the centromedial amygdala and the bed nucleus of the stria terminalis.

Molecular characterization of immunoreactivities of peptides derived from chromogranin A (GE-25) and from secretogranin II (secretoneurin) in human and bovine cerebrospinal fluid

Chromogranin A and secretogranin II are members of the so-called chromogranins, the acidic proteins stored in neuroendocrine large dense-core vesicles. We characterized chromogranin A and secretogranin II immunoreactivities in cerebrospinal fluid by radioimmunoassays using synthetic peptides derived from these components (GE-25 for chromogranin A and secretoneurin for secretogranin II). In lumbar cerebrospinal fluid, high levels (more than 1000 fmol/ml) of these two components were found, whereas in ventricular cerebrospinal fluid the secretoneurin levels were relatively low. The cerebrospinal fluid/serum ratio for secretoneurin was close to 170. High-performance liquid chromatography revealed that in both cerebrospinal fluid and extracts from human brain secretoneurin was the predominant immunoreactive component. In cerebrospinal fluid chromogranin A immunoreactivity was present as intermediate-sized peptides with little intact chromogranin A and free GE-25 peptide. In human brain samples smaller peptides including GE-25 were more predominant. Analogous findings for secretoneurin and chromogranin A were obtained for bovine brain samples. We can conclude that chromogranins are present in cerebrospinal fluid in concentrations much higher than those of classical neuropeptides also stored in large dense-core vesicles. Therefore, their degree of proteolytic processing can be analysed with small samples of cerebrospinal fluid. A possible disturbance of proteolytic processing in large dense-core vesicles in various pathological conditions can now be discovered.

Immunohistochemistry of small intensely fluorescent (SIF) cells and of SIF cell-associated nerve fibers in the rat superior cervical ganglion

Double-labelling immunofluorescence was applied on single sections of the rat superior cervical ganglion to evaluate neurochemistry and connectivity of intraganglionic SIF cells. The synaptic vesicle membrane protein synaptophysin and secretoneurin, a newly discovered neuropeptide derived from secretogranin II, proved reliable molecular markers of this cell type, whereas serotonin and tyrosine hydroxylase immunoreactivities were observed in slightly incongruent SIF cell subpopulations. Immunolabelling for vasoactive intestinal polypeptide and neuropeptide Y occurred in few SIF cells. None of the above immunoreactivities were visibly altered by preganglionic or postganglionic denervation, while some SIF cells were immunolabelled for galanin or for the neuronal microtubule-associated protein MAP2 after postganglionic denervation. SIF cells were nonreactive for the pan-neuronal marker protein gene product (PGP) 9.5 or neurofilament 160 kD. Intense staining of NADPH-diaphorase in some SIF cells, suggesting catalytic activity of nitric oxide synthase, could not be substantiated by immunoreactivity for this enzyme. SIF cells were approached by nonidentical fiber populations immunoreactive for PGP 9.5, neurofilament, or neuropeptide Y, whereas immunoreactivities for galanin and vasoactive intestinal polypeptide were colocalized in fiber meshes around SIF cells. The findings indicate (1) neurochemical SIF cell heterogeneity, (2) SIF cell plasticity in response to ganglionic perturbation, and (3) a differentiated innervation of SIF cells in the rat superior cervical ganglion.

Expression of chromogranin A and B and secretoneurin immunoreactivity in neoplastic and nonneoplastic pancreatic alpha cells

In the endocrine pancreas, chromogranins A and B as well as secretoneurin (a biologically active peptide processed endoproteolytically from secretogranin II) are most intensely expressed in alpha (glucagon) cells. We examined whether the functional status of neoplastic and nonneoplastic human alpha cells is reflected in the expression patterns of chromogranins/secretogranins. Neoplastic alpha cells were analysed immunocytochemically in six functioning glucagonomas and 37 nonfunctioning neuroendocrine tumours (29 with alpha cells) for their immunoreactivity to chromogranin A and B, as well as secretoneurin. There was no difference in the staining intensity for either peptide between glucagonomas and nonfunctioning, alpha cell containing tumours. Nonneoplastic alpha cells from patients with a functioning glucagonoma showed a decreased glucagon immunoreactivity, whereas the expression of chromogranin A (but not chromogranin B and secretoneurin) was as intense as in alpha cells not associated with glucagonoma syndrome. These results suggest that the expression of chromogranins/secretogranins in neoplastic alpha cells of the pancreas may be independently regulated from the cells' functional status. In nonneoplastic alpha cells there seems to be an association between glucagon production and chromogranin B and secretoneurin expression.

Large dense-core vesicles in rat adrenal after reserpine: levels of mRNAs of soluble and membrane-bound constituents in chromaffin and ganglion cells indicate a biosynthesis of vesicles with higher secretory quanta

Rats were injected with a large dose of reserpine known to stimulate the adrenal medulla. Various times after drug treatment the mRNA levels of several constituents of large dense-core vesicles were determined by northern blot analysis and in situ hybridization. The latter method allowed detection of changes in mRNA levels not only in chromaffin cells, but also in the ganglion cells found in adrenal medulla. Levels of the mRNAs of secretory components of large dense-core vesicles (chromogranins A and B, secretogranin II, VGF, and neuropeptide Y) increased in chromaffin cells by 215-857% after 1-3 days of drug treatment. For partly membrane-bound components (dopamine beta-hydroxylase, prohormone convertase 2, carboxypeptidase H, and peptidylglycine alpha-amidating monooxygenase) the changes ranged from 182 to 315%, whereas for glycoprotein III and for intrinsic membrane proteins (cytochrome b561 and vesicle monoamine transporter 2) no change occurred. In ganglion cells the mRNAs that could be detected for VGF, neuropeptide Y, secretogranin II, carboxypeptidase H, and vesicle monoamine transporter 1 showed an analogous pattern of change, with significant increases for the secretory proteins and no change for the membrane components. From these and previous results we suggest the following concept: Long-lasting stimulation of chromaffin cells or neurons does not induce the biosynthesis of a larger number of vesicles but rather leads to the formation of vesicles containing higher secretory quanta of chromogranins and neuropeptides.

Release of secretoneurin and noradrenaline from hypothalamic slices and its differential inhibition by calcium channel blockers

Secretoneurin is a newly discovered peptide found in high concentrations in brain. We have studied the release of secretoneurin and noradrenaline from superfused hypothalamic slices from rat brain. Both electrical stimulation and potassium induced depolarisation released secretoneurin and noradrenaline from these slices in a calcium-dependent manner. Electrical stimulation caused a preferential release of noradrenaline when compared to the secretion elicited by high potassium. The time course of secretoneurin release was more protracted than that of noradrenaline. The calcium channel blocker omega-conotoxin inhibited only the electrically induced release of noradrenaline, whereas nifedipine inhibited only that of secretoneurin. These results establish that secretoneurin is secreted from neurons. Inhibition of this release by nifedipine is consistent with the concept that secretion from large dense core vesicles occurs at sites different from that of small vesicles and depends on calcium influx via L-type calcium channels.

Human and rat primary C-fibre afferents store and release secretoneurin, a novel neuropeptide

Secretoneurin is a recently discovered neuropeptide derived from secretogranin II (SgII). Since this peptide could be detected in the dorsal horn of the spinal cord we studied whether it is localized in and released from primary afferent neurons. Secretoneurin was investigated with immunocytochemistry and radioimmunoassay in spinal cord, dorsal root ganglia and peripheral organs. SgII mRNA was determined in dorsal root ganglia. Normal rats and rats pre-treated neonatally with capsaicin to destroy selectively polymodal nociceptive (C-) fibres were used. Slices of dorsal spinal cord were perfused in vitro for release experiments. Immunocytochemistry showed a distinct distribution of secretoneurin-immunoreactivity (IR) in the spinal cord and, lower brainstem. A particularly high density of fibres was found in lamina I and outer lamina II of the caudal trigeminal nucleus and of the spinal cord. This distribution was qualitatively identical in rat and human post-mortem tissue. Numerous small diameter and some large dorsal root ganglia neurons were found to contain SgII mRNA. Capsaicin treatment led to a marked depletion of secretoneurin-IR in the substantia gelatinosa, but not in other immunopositive areas of the spinal cord and to a substantial loss of small (< 25 microns) SgII-mRNA-containing dorsal root ganglia neurons. Radioimmunoassay revealed a significant decrease of secretoneurin-IR in the dorsal spinal cord, the trachea, heart and urinary bladder of capsaicin-treated rats. Perfusion of spinal cord slices with capsaicin as well as with 60 mM potassium led to a release of secretoneurin-IR. In conclusion, secretoneurin is a neuropeptide which is stored in and released from capsaicin-sensitive, primary afferent (C-fibre) neurons.(ABSTRACT TRUNCATED AT 250 WORDS)

Immunohistochemical demonstration of chromogranin A, chromogranin B, and secretogranin II in extra-adrenal paragangliomas

Twelve sympathetic and 14 parasympathetic extra-adrenal paragangliomas were investigated immunohistochemically with antibodies against chromogranin A, chromogranin B, and secretogranin II. In sympathetic paragangliomas chromogranin A was found in 12/12 and chromogranin B in 11/12 tumors in almost all chief cells (the remaining tumor was focally chromogranin B positive), whereas secretogranin II was immunolocalized in the majority of chief cells in 5/12, in a focal distribution in 3/12, and only in a few scattered tumor cells in 3/12 cases. One case showed no secretogranin II immunoreactivity. In parasympathetic paragangliomas both chromogranin B and secretogranin II immunoreactivity was demonstrated in the majority of chief cells of all 14 tumors investigated. Chromogranin A showed a strong immunostaining in 2/14 cases; in 12 tumors chromogranin A was found in only a few chief cells or was completely absent. It is concluded that sympathetic and parasympathetic paragangliomas show a divergent expression of chromogranins/secretogranins that apparently reflects the different histogenetic origins of these tumors.

Immunohistochemical localization of chromogranins A and B and secretogranin II in normal, hyperplastic and neoplastic prostate

Routinely processed normal, hyperplastic and neoplastic prostatic tissue was immunohistochemically investigated with antibodies against chromogranin A and B and secretogranin II. In normal and hyperplastic prostates all three peptides were immunolocalized in scattered neuroendocrine cells situated within the glandular epithelium. In 17 prostatic carcinomas with pronounced neuroendocrine differentiation and in a case of prostatic carcinoid, chromogranin B was the major component whereas chromogranin A and secretogranin II were virtually absent in poorly differentiated (grade III) tumours. Neuroendocrine differentiation in prostatic cancer is most likely to be associated with a poor clinical outcome; thus, chromogranin B appears to be a useful marker in the histopathological diagnosis of these neoplasms.

Distribution of secretoneurin immunoreactivity in the spinal cord and lower brainstem in comparison with that of substance P and calcitonin gene-related peptide

Secretoneurin is a peptide of 33 amino acids generated in brain by proteolytic processing of secretogranin II. The distribution of this newly characterized peptide was investigated by means of immunocytochemistry and in situ hybridization in the spinal cord and lower brainstem of the rat. The staining pattern of secretoneurin immunoreactivity (IR) was compared to that of substance P (SP) and calcitonin gene-related peptide (CGRP) in adjacent sections. A high density of secretoneurin-IR fibers and terminals was found in lamina I and outer lamina II of the caudal trigeminal nucleus and of the spinal cord at all levels, around the central canal, and in the sympathetic and parasympathetic areas of the lateral cell columns. The ventral horn displayed a low to moderate density of secretoneurin-IR. The highest number of secretogranin II mRNA-containing cells was found in lamina II of the dorsal horn and in neurons of the dorsal root ganglia. In the white matter, secretoneurin-IR was most prominent in the dorsolateral part of the lateral funiculus and in the tract of Lissauer. The distributions of secretoneurin-IR and SP-IR were strikingly similar. CGRP-IR and secretoneurin-IR overlapped in the outer laminae of the dorsal horn, in the lateral cell column, and probably in some motoneurons. This study establishes that, like SP and CGRP, secretoneurin is a peptide highly concentrated in the terminal field of primary afferents and in sympathetic and parasympathetic areas. Thus secretoneurin might be involved in the modulation of afferent transmission.

Bovine posterior pituitary: presence of p65 (synaptotagmin), PC1, PC2 and secretoneurin in large dense core vesicles

The subcellular distribution of p65 (synaptotagmin), of the endoproteases PC1 and PC2 and of secretoneurin was studied in bovine posterior pituitary by differential and density gradient centrifugation. All these peptides were found to be present in the neurosecretory granules (large dense core vesicles). p65 can therefore participate not only in exocytosis from small synaptic vesicles but also from large dense core vesicles. Secretoneurin is a peptide derived from secretogranin II. Processing of the propeptide apparently occurs during axonal transport of the large dense core vesicles and is complete in the posterior pituitary. Thus, stimulation of the hypothalamic magnocellular neurons can lead to the release of this newly characterized, functional neuropeptide.

Distribution of secretoneurin-like immunoreactivity in comparison with substance P- and enkephalin-like immunoreactivities in various human forebrain regions

The distribution of secretoneurin-like immunoreactivity, a peptide derived from secretogranin II, was studied by means of immunocytochemistry and compared to the pattern of staining for substance P- and enkephalin-like immunoreactivities in the human basal forebrain, with special reference to the basal ganglia. Secretoneurin-like immunoreactivity was characterized by gel filtration and reversed-phase high pressure liquid chromatography analysis. Chromatographic analysis revealed a single peak for secretoneurin-like immunoreactivity. No secretoneurin-immunopositive forms of high molecular weight were found. Secretoneurin-like immunoreactivity appeared mainly in dot- and fibre-like structures. In addition, a band-like terminal staining (woolly fibres) that has been shown by others for substance P- and enkephalin-like immunoreactivities, was also observed for secretoneurin-like immunoreactivity. Medium-sized cells were found arranged in clusters or singly within the caudate and putamen. In the basal ganglia, a high density of secretoneurin-like immunoreactivity was found in the internal segment of the globus pallidus, the ventral pallidum and in the pars reticulata of the substantia nigra. In these areas the immunostaining appeared mainly as woolly fibres. The bed nucleus of the stria terminalis and medial amygdala displayed a high density of fine beaded secretoneurin-like immunoreactive fibres, sometimes forming pericellular contacts. The nucelus basalis of Meynert was highly innervated by secretoneurin-like immunoreactive fibres, mainly in the form of woolly fibres. In general, a large overlap was found between secretoneurin- and substance P-like immunoreactivity in all examined areas of the basal ganglia. In the bed nucelus of the stria terminalis and medial amygdala secretoneurin-like immunoreactivity was distributed very similarly to enkephalin-like immunoreactivity. These data provide evidence that in different subsets of neurons and neuronal pathways secretoneurin-like immunoreactivity coexists with substance P- and enkephalin-like immunoreactivity in several areas of the human brain.

Ontogenic development and distribution of mRNAs of chromogranin A and B, secretogranin II, p65 and synaptin/synaptophysin in rat brain

We have studied by in situ hybridization the mRNA levels of several constituents of transmitter storing vesicles during ontogenic development of rat brain. The following vesicle components were investigated: chromogranin A and B and secretogranin II, representing secretory peptides of large dense core vesicles, and the membrane proteins p65 and synaptin/synaptophysin which are found in both large and small synaptic vesicles but are concentrated in the latter ones. Several ontogenic patterns were observed: concomitant increases of most or all mRNAs in certain brain regions, e.g. in the thalamic nuclei at gestational day 18 or in the cortex at postnatal day 6. For some areas selective increases for the various chromogranin mRNAs occurred, thus throughout development the substantia nigra compacta contained only the chromogranin B mRNA, whereas the lateral and medial geniculate nuclei and the medial tuberal nucleus expressed only secretogranin II mRNA. In the paraventricular hypothalamic nucleus, secretogranin II mRNA declined at P1 and then increased again. In the intermediate cortex there was a rather selective appearance of a high level of chromogranin A mRNA already at gestational day 16. In general the mRNAs for the membrane components become detectable by in situ hybridization together with the chromogranin mRNA, however, in the claustrum a high level of the p65 mRNA is present already at gestational day 16 whereas the chromogranin mRNA only appears at day 20. In some nuclei there was also a differential expression of the membrane components with e.g. the synaptophysin mRNA being present without any concomitant appearance of p65. These results establish that the ontogenic development of the investigated components in many brain areas simply indicate the starting point of biosynthesis of both types of vesicles finally leading to functional synapses. In those cases where a selective dissociation in the biosynthesis of these components occurs, a functional relevance of one component for a certain stage of development might be postulated. Since these data define the time of onset of vesicle biosynthesis in the various brain regions, future studies on single components of these vesicles can be interpreted in the context of the present findings.

Attraction of human monocytes by the neuropeptide secretoneurin

Secretoneurin is a newly discovered 33-amino-acid peptide derived from secretogranin II (chromogranin C) that is found in sensory afferent C-fibers. We show here that secretoneurin triggers the selective migration of human monocytes in vitro and in vivo. Combinations of secretoneurin with the sensory neuropeptides, substance P or somatostatin, synergistically stimulate such migration. The attraction of monocytes represents the first established function of secretoneurin as a sensory neuropeptide.

Messenger RNA levels of chromogranin B, secretogranin II, and VGF in rat brain after AF64A-induced septohippocampal cholinergic lesions

The mRNA levels of secretogranin II, chromogranin B, and VGF were compared in brains of control and AF64A-treated rats. This toxin induces specific lesions of the septohippocampal cholinergic pathway. As a consequence of this treatment, the chromogranin B message was elevated in the dentate gyrus granule cells of the hippocampus. In the paraventricular nucleus of the hypothalamus, a concomitant elevation of the messages of secretogranin II and corticotropin-releasing factor occurred in the parvocellular neurons, and an increase of those of secretogranin II and VGF occurred in a subgroup of magnocellular neurons. Further increases for secretogranin II were seen in the amygdaloid nuclei and the reticular thalamic nuclei and increases for chromogranin B in the temporal cortex, substantia nigra compacta, and ventral tegmental area. These results indicate that the toxin-induced lesion of the cholinergic pathway innervating the hippocampus apparently leads to the stimulation of several defined groups of neurons that react with an increase in the mRNA levels of their secretory peptides. We suggest that changes in mRNA expression of these peptides are useful parameters for defining neurons under chronic stimulation.

Kainic acid seizures in the rat: differential expression of chromogranin A, carboxypeptidase H and peptidylglycine alpha-amidating monooxigenase in subfields of the hippocampal formation

Using in situ hybridization histochemistry concentrations of mRNAs encoding chromogranin A (ChA), carboxypeptidase H (CPH) and peptidylglycine alpha-amidating monooxigenase (PAM) have been investigated in the hippocampus after kainic acid (KA)-induced limbic seizures in the rat. Increased concentrations (by 150%) of ChA and CPH mRNAs were found in the granule cell layer 24 h after KA injection. At the same time PAM mRNA levels were only slightly elevated (by 50%). Whereas the increases in CPH and PAM transcripts were only transient, ChA mRNA concentrations in the granule cell layer were elevated up to 2 months after the initial seizures. In contrast, in the pyramidal cell layers of all hippocampal subfields (CA1 to CA3) ChA mRNA concentrations were significantly reduced (by 40-70%) 1-60 days after KA. PAM and CPH messages were slightly reduced in the pyramidal cell layer of CA1 but not in CA2 and CA3. The experiments demonstrate that KA-induced limbic seizures cause sustained changes in the expression of ChA mRNA. At the same time the expression of two enzymes involved in post-translational processing of neuropeptides, PAM and CPH, becomes only transiently altered. Synthesis of ChA may be regulated differently in the strata granulosum and pyramidale during epileptic seizures.

Glycoprotein III (clusterin, sulfated glycoprotein 2) in endocrine, nervous, and other tissues: immunochemical characterization, subcellular localization, and regulation of biosynthesis

Specific antisera were raised against the A and B chains of glycoprotein III. Immunoblotting revealed that in adrenal medulla both chains migrate very closely together in two-dimensional electrophoresis. Both chains with slightly differing molecular sizes are found in several endocrine tissues and in brain, kidney, liver, and serum. The mRNA has an analogous widespread distribution. In primary cultures of chromaffin cells the level of message becomes significantly increased by treatment with histamine or 12-O-tetradecanoylphorbol 13-acetate/forskolin. However, the increase is small when compared with that of secretogranin II. The subcellular localization of glycoprotein III in endocrine organs and in the posterior pituitary was investigated by subcellular fractionation and immunoelectron microscopy. Glycoprotein III was found to be confined to the large dense-core vesicles of these organs. For a discussion of the function of glycoprotein III, its localization in these organelles has to be taken into account.

Different degrees of processing of secretogranin II in large dense core vesicles of bovine adrenal medulla and sympathetic axons correlate with their content of soluble PC1 and PC2

We investigated the processing of secretogranin II in large dense core vesicles of adrenal medulla and sympathetic nerve. Despite the fact that both types of vesicles have a very similar biochemical composition, the degree of processing of secretogranin II in vesicles from splenic nerve was significantly higher. The endoproteases PC1 and PC2, two likely candidates for secretogranin II cleavage, are found in both types of vesicles, however, relative to secretogranin II the nerve vesicles have a much higher content of these enzymes. This probably explains the fast and more extensive processing of secretogranin II in these vesicles.

Reserpine causes differential changes in the mRNA levels of chromogranin B, secretogranin II, carboxypeptidase H, alpha-amidating monooxygenase, the vesicular amine transporter and of synaptin/synaptophysin in rat brain

Brains of rats treated with a high dose of reserpine were analyzed by in situ hybridization. The mRNA levels of several components of large dense core and small synaptic vesicles were determined. After drug treatment the secretogranin II message was elevated in the parvocellular neurons of the paraventricular nucleus, in the zona incerta, dorsal raphe, locus coeruleus and in the nucleus tractus solitarius. The levels of chromogranin B mRNA were increased in the dorsal raphe and in the substantia nigra compacta. In control animals messages for synaptin/synaptophysin could be found in most of the nuclei investigated, that of the vesicular amine transporter was only detectable in substantia nigra compacta, the dorsal raphe and the locus coeruleus whereas those of carboxypeptidase H and the alpha-amidating monooxygenase could only be determined in the paraventricular nucleus. All these messages were not changed after reserpine. We conclude that the chromogranin B/secretogranin II messages are regulated concomitantly with various neuropeptides. They represent useful general markers to identify stimulated neurons. Our results are consistent with the concept that stimulation of neurons leads to an increased synthesis of secretory peptides and consequently to large dense core vesicles filled with higher quanta of peptides.

Vesicle monoamine transporters 1 and 2: differential distribution and regulation of their mRNAs in chromaffin and ganglion cells of rat adrenal medulla

The expression and synthesis regulation of the vesicle monoamine transporter was investigated in rat adrenal medulla. Previous studies established two genes for monoamine transporters by molecular techniques. In rat adrenal medulla, a differential expression of the corresponding mRNAs was found by in situ hybridization. The mRNA of monoamine transporter 2 was localized in chromaffin cells whereas monoamine transporter 1 mRNA occurred only in ganglion cells of the adrenal medulla. Insulin-induced hypoglycemia, a model for short neurogenic stimulation of the adrenal medulla, did not alter steady-state mRNA levels of both monoamine transporters.

Concomitant changes of messenger ribonucleic acid levels of secretogranin II, VGF, vasopressin and oxytocin in the paraventricular nucleus of rats after adrenalectomy and during lactation

In situ hybridization was used to study the mRNA levels for secretogranin II and VGF in comparison with those of oxytocin and vasopressin in the hypothalamus of rats. VGF is a widespread constituent of large dense core vesicles which is selectively induced in PC12 cells by nerve growth factor. After adrenalectomy the mRNA levels of secretogranin II, VGF and vasopressin were increased 4- to 5-fold in the parvocellular neurons of the paraventricular nuclei. In lactating rats the message for oxytocin and secretogranin II were significantly elevated in the magnocellular neurons of the paraventricular and supraoptic nuclei, whereas for VGF only a smaller non-significant increase was observed. As shown by immunoelectron microscopy secretoneurin (a peptide derived from secretogranin II) and oxytocin are co-stored in the large dense core vesicles of the hypothalamo-neurohypophysial neurons. These results demonstrate that stimulation of both parvo- and magnocellular neurons of the hypothalamus induces a concomitant increase of the messages for secretogranin II and VGF together with those of vasopressin and oxytocin.

Secretogranin II is synthesized and secreted in astrocyte cultures

Astrocyte cultures from rat brain were analyzed for their ability to synthesize and secrete secretogranin II (chromogranin C). Northern blot analysis of polyA-selected RNA established the presence of secretogranin II mRNA in these cells. By radioimmunoassay, 11.6 fmol/10(6) astrocytes of secretogranin II was found in these cells. About twice the amount was released into the medium within 3 days. Secretogranin II within the astrocytes was practically unprocessed, as shown by HPLC. These results establish for the first time that astrocytes in vitro synthesize and secrete a protein of the acidic chromogranin family.

Chromogranin A, secretogranin II and vasoactive intestinal peptide in phaeochromocytomas and ganglioneuromas

By means of immunohistochemistry we analysed the distribution of chromogranin A, secretogranin II and vasoactive intestinal peptide (VIP) in 16 phaeochromocytomas, two cases of combined phaeochromocytoma-ganglioneuroma and four adrenal ganglioneuromas. Chromogranin A was found in the majority of phaeochromocytes and in mixed phaeochromocytomas-ganglioneuromas. Secretogranin II was present to a lesser degree in phaeochromocytes, but strong immunostaining was found in most ganglion cells of phaeochromocytomas, in the ganglioneuroma component of combined tumours and in adrenal ganglioneuromas. Vasoactive intestinal peptide was present in some ganglion cells of phaeochromocytomas, in the ganglioneuroma component of mixed tumours and in three of four adrenal ganglioneuromas. On semi-adjacent sections a co-localization of VIP and secretogranin II was demonstrated. These results indicate that neuronal differentiation is accompanied by an increased immunohistochemical expression of secretogranin II. Therefore, secretogranin II may be a useful marker for ganglion cell differentiation.

Distribution of secretoneurin, a peptide derived from secretogranin II, in rat brain: an immunocytochemical and radioimmunological study

The distribution of secretoneurin, a peptide derived from its precursor secretogranin II by proteolytic processing, was studied in the central nervous system of the rat by immunocytochemistry and radioimmunoassay and compared to the distribution of secretogranin II messenger RNA by using in situ hybridization. With a specific antiserum a distinct staining of fibers and to a lesser extent also of perikarya was observed throughout the central nervous system. A high density of immunoreactive fibers and terminals was found in several brain areas, i.e. the lateral septum, the medial parts of the amygdala, some medial thalamic nuclei, the hypothalamus, habenula, nucleus interpeduncularis, locus coeruleus, nucleus tractus solitarii, the substantiae gelatinosae of the caudal trigeminal nucleus and of the spinal cord. The quantitative distribution as measured by a radioimmunoassay agreed well with the varying densities of immunoreactivity found by immunocytochemistry. The highest concentrations of this peptide were present in the hypothalamus, in particular, in the median eminence and are comparable to those of the most highly concentrated neuropeptides. The distribution of immunopositive perikarya corresponded well with that of secretogranin II messenger RNA obtained by in situ hybridization. The pattern of secretoneurin expression in rat brain was widespread and unique, partially overlapping with established chemical transmitters and neuropeptides. The functional significance of this new brain peptide remains to be established.

Secretoneurin releases dopamine from rat striatal slices: a biological effect of a peptide derived from secretogranin II (chromogranin C)

Proteolytic processing of secretogranin II (chromogranin C) in brain leads to the formation of a 33-amino acid peptide which we have named secretoneurin. All the properties of secretoneurin are consistent with the concept that this peptide represents a neuropeptide. However, a biological function has not yet been demonstrated. Therefore, we have now investigated whether secretoneurin could alter transmitter release in brain. Slices of rat caudate-putamen were superfused in an in vitro system and dopamine was measured in the superfusate. Secretoneurin dose-dependently increased the outflow of dopamine. This response was abolished in Ca(2+)-free medium. The secretoneurin-response could also be blocked by preincubation of the peptide with a specific antiserum and was subject to rapid specific and reversible desensitization. This effect on dopamine release constitutes the first discovered biological effect found for a peptide derived from secretogranin II. Thus, secretoneurin can be added to the ever-growing number of neuropeptides.

In situ hybridization: mRNA levels of secretogranin II, VGF and peptidylglycine alpha-amidating monooxygenase in brain of salt-loaded rats

The mRNA levels of secretogranin II (SgII), VGF and peptidylglycine alpha-amidating monooxygenase (PAM) were studied in brains of salt loaded rats by in situ hybridization. In these rats the levels of the message for secretogranin II and VGF were increased in the paraventricular, supraoptic and retrochiasmatic nuclei and in the subfornical organ. The increases ranged from 416 to 721% for SgII and from 778 to 890% for VGF. The PAM message was also elevated in these brain regions; however, the maximal increase was only 221%. We conclude that the message for all secretory peptides investigated so far, i.e. vasopressin, galanin, secretogranin II and VGF are upregulated to a similar degree in the hypothalamus of salt-located rats. The relative increase in mRNA for the enzyme peptidylglycine alpha-amidating monooxygenase occurred to a much lower extent, and was comparable to the limited changes previously seen for carboxypeptidase H.

Secretoneurin--a neuropeptide generated in brain, adrenal medulla and other endocrine tissues by proteolytic processing of secretogranin II (chromogranin C)

Secretogranin II (chromogranin C), originally described as tyrosine sulfated protein of the anterior pituitary, is present in large dense core vesicles of several endocrine cells and neurons. We raised antisera in rabbits to conjugates of two synthetic peptides (bovine secretogranin 133-151 and rat secretogranin 154-186) flanked in the primary structure of secretogranin II by pairs of basic residues and used them to investigate the proteolytic processing of this protein by immunoblotting and a newly developed radioimmunoassay. The sensitivity of this assay was 30 fmol for secretogranin 154-186 and 60 fmol for secretogranin 133-151. The highest degree of processing of secretogranin II (> 90%) occurs in brain. One of the peptides (secretogranin 133-151) is not generated to any significant extent. The other peptide, secretogranin 154-186, however, is formed in vivo, and in brain the free peptide apparently represents the predominant form. The highest concentrations of secretogranin 154-186 are found in the hypothalamus, two- to six-fold lower levels are present in the hippocampus, caudate nucleus, thalamus and brainstem. These concentrations are comparable to those of established neuropeptides. In order to indicate the special relevance of secretogranin II and of this peptide for brain we have named this peptide secretoneurin. The newly developed radioimmunoassay for this peptide will be a useful tool to establish its physiologic role in brain.

Histamine induces a gene-specific synthesis regulation of secretogranin II but not of chromogranin A and B in chromaffin cells in a calcium-dependent manner

The effect of histamine on steady-state mRNA levels of three soluble secretory proteins from chromaffin granules was investigated in cultured bovine adrenal medullary cells. Histamine stimulated secretogranin II mRNA 4-fold, with no or only slight effects on chromogranin A and B transcription. After an initial lag phase, secretogranin II mRNA increased markedly between 4 and 12 h followed by a plateau phase up to 48 h. The effect of histamine on secretogranin II gene-expression was abolished by the H1 receptor antagonist promethazine but not by the H2 blocker cimetidine. The histamine-induced elevation of secretogranin II mRNA was partially reduced by the L-type calcium channel blocker nifedipine, indicating a contribution of extracellular calcium in the second messenger signaling pathway involved. At present, the H1 histaminergic receptor is the first membrane receptor found regulating secretogranin II biosynthesis in chromaffin cells. The selective up-regulation of secretogranin II mRNA but not of chromogranin A and B by histamine is another example illustrating that the synthesis regulation of secretory components co-stored in large vesicles of neuroendocrine cells is specific to the individual gene. Together with results obtained earlier, our data demonstrate a marked variation in the relative composition of peptides secreted from adrenal medulla into circulation following different physiologic conditions.

Temporal lobe epilepsy of the rat: differential expression of mRNAs of chromogranin B, secretogranin II, synaptin/synaptophysin and p65 in subfield of the hippocampus

We have investigated by in situ hybridization changes in the content of mRNAs encoding for chromogranin B, secretogranin II, synaptin/synaptophysin and p65 after kainic acid-induced seizures and pentylenetetrazol kindling. Kainic acid seizures resulted in marked but transient increases in secretogranin II mRNA concentrations in the granule cell layer and throughout the pyramidal cell layers of the hippocampus (by 100-500%) as well as in various areas of the cerebral cortex (by up to 900%) and the thalamus (up to 300%) 12 h after injection of the toxin. Chromogranin B mRNA concentrations were persistently increased in granule cells (but not in pyramidal cells) of the hippocampus (suprapyramidal blade, 450%) and in cortical areas (250%) at all time intervals after kainic acid injection (12 h to 60 days). Accordingly chromogranin B immunoreactivity was enhanced in the terminal field of mossy fibers and in the inner part of the molecular layer 30 days after kainic acid. Secretogranin II immunoreactivity was also markedly increased in CA1, the paraventricular thalamic nucleus and in the central amygdala. In rats kindled with pentylenetetrazol only chromogranin B (by 200%) but not secretogranin II mRNA was increased in dentate granule cells. In contrast to the mRNAs of these secretory proteins concentrations of mRNAs encoding synaptin/synaptophysin and p65, two membrane proteins of synaptic vesicles, were not altered in any of these brain structures. These data demonstrate that in brain the biosynthesis of chromogranin B and secretogranin II is regulated like that of neuropeptides which is consistent with a role of these secretory polypeptides as precursors of functional peptides. Activation of neurons induces an increased synthesis of neuropeptides but not a concomitant synthesis of membrane proteins of synaptic vesicle. This might lead to an increased quantal content available for transmission.

Secretogranin II expression in Ewing's sarcomas and primitive neuroectodermal tumors

Production of chromogranins, the acidic components of the chromaffin granules regarded as specific neuroendocrine markers, was analyzed by immunocytochemistry and hybridization (Northern blotting and in situ hybridization) in primary lesions and cell lines of Ewing's sarcomas, primitive neuroectodermal tumors (PNETs), and neuroblastomas. Antibodies and probes specific for chromogranin A (CgA), chromogranin B (CgB), and secretogranin II (SgII) were used. Ewing's sarcomas and PNETs, unlike neuroblastomas, were negative for CgA and CgB. Two primary Ewing's sarcomas, one primary PNET (an Askin tumor), and one PNET cell line (TC32) were found to strongly express the SgII gene, as shown by the presence of specific mRNA. This result supports the hypothesis that some Ewing's sarcomas represent a most primitive form of neuroectodermal tumor; in addition, it indicates a diagnostic role of SgII in cases of Ewing's sarcomas and PNETs.

Proinflammatory cytokines in cardiac myxomas

Serum levels of various cytokines were measured in three patients with cardiac myxomas presenting with and without constitutional symptoms, immunological features and elevated plasma levels of interleukin-6. Interleukin-6 but not other cytokines (interleukin-1, tumour necrosis factor-alpha, interferon-gamma) relate to immunological features of the patients. Circulating levels of atrial natriuretic peptide correspond to haemodynamic changes but not to the tumour-bearing state itself.

Immunohistochemical comparison of chromogranins A and B and secretogranin II with calcitonin and calcitonin gene-related peptide expression in normal, hyperplastic and neoplastic C-cells of the human thyroid

Normal and hyperplastic thyroid C-cells and 14 cases of medullary thyroid carcinoma were investigated immunohistochemically with antibodies against chromogranins A and B, secretogranin II, calcitonin and calcitonin gene-related peptide (CGRP). Normal and hyperplastic C-cells showed strong calcitonin and chromogranin A immunoreactivity whereas CGRP, chromogranin B and secretogranin II expression was less intense. Strong calcitonin and chromogranin A immunoreactivity was also found in the majority of tumour cells in medullary thyroid carcinoma. The CGRP, chromogranin B and secretogranin II staining observed was present in variable patterns. In some cases CGRP, chromogranin B and secretogranin II could only be demonstrated in isolated tumour cells with elongated processes suggestive of neuronal differentiation of these cells. The biological function(s) of the chromogranins/secretogranins remain(s) still unclear. There is evidence that these proteins are pro-peptides which give rise to functionally active compounds. Studies on normal C-cells and medullary thyroid carcinoma may elucidate the role of chromogranins/secretogranins in endocrine and neuronal cells.

Differential subcellular distribution of PC1, PC2 and furin in bovine adrenal medulla and secretion of PC1 and PC2 from this tissue

The subcellular distribution of PC1, PC2 and furin was determined in bovine adrenal medulla by immunoblotting of fractions obtained by density gradient centrifugation. PC1 and PC2 were found to be confined to chromaffin granules whereas furin (C-terminal-peptide) was absent from these organelles. Stimulation of bovine adrenal medulla by carbamoylcholine chloride induced the secretion of PC1 and PC2. The secreted enzymes had the same molecular size as PC1 and PC2 present in chromaffin granules.

Transsynaptic regulation of galanin, neurotensin, and substance P in the adrenal medulla: combinatorial control by second-messenger signaling pathways

The adrenomedullary content of neurotensin and substance P was examined 1, 6, and 12 days after hypoglycemic shock. The neurotensin content was increased 60-fold within 24 h and remained elevated for up to 12 days, whereas the substance P content was increased approximately sevenfold within 24 h of insulin treatment and returned to control levels by 12 days poststimulation. Because protein kinase A, protein kinase C, and calcium influx in the rat adrenal medulla are all stimulated following splanchnic nerve stimulation, the differential regulation of neurotensin and substance P biosynthesis following stimulation of these three pathways was examined in bovine chromaffin cells in vitro. Neurotensin levels were up-regulated by elevated potassium, forskolin, and phorbol ester in bovine chromaffin cells. Substance P levels were up-regulated by elevated potassium and forskolin but not by phorbol ester treatment. When chromaffin cells were treated with phorbol ester in combination with forskolin, neurotensin levels were increased in a synergistic fashion, whereas phorbol ester antagonized the forskolin-induced elevation of substance P levels. Earlier, it was reported that galanin biosynthesis, like neurotensin biosynthesis, is upregulated by depolarization, phorbol ester stimulation, and forskolin treatment in chromaffin cells in vitro. Here we report that galanin is also, like neurotensin, increased greater than 60-fold after stimulation of the rat adrenal medulla in vivo. Neuropeptide-specific combinatorial effects of stimulating the calcium, protein kinase A, and protein kinase C signaling pathways may underlie the quantitative differences between galanin and neurotensin compared with substance P up-regulation in rat adrenal medulla after splanchnic nerve stimulation in vivo.

In situ hybridization: mRNA levels of secretogranin II, neuropeptides and carboxypeptidase H in brains of salt-loaded and Brattleboro rats

In situ hybridization was used to study the mRNA levels for vasopressin, galanin, secretogranin II and carboxypeptidase H in salt-loaded and Brattleboro rats. These animals represent an in vivo model for the chronic stimulation of the hypothalamo-neurohypophyseal neurons. As shown by immunelectron microscopy secretogranin II is co-stored with vasopressin in these neurons. In salt-loaded rats the levels of mRNA for vasopressin, galanin and secretogranin II are increased in the paraventricular and supraoptic nuclei. Analogous changes were observed for Brattleboro rats with the exception of the vasopressin message which was decreased in these animals. The secretogranin II message was also increased in neurons which do not contain the vasopressin mRNA, i.e. in magnocellular neurons of the lateral hypothalamus and in the subfornical organ. Carboxypeptidase H message was also found in the paraventricular and supraoptic nuclei and in the subfornical organ; however, in both models the changes in mRNA in these nuclei were much lower than those observed for the secretory peptides or non-existent. We conclude that chronic stimulation of vasopressin neurons leads to a concomitant up-regulation of the biosynthesis of neuropeptides and secretogranin II. We suggest that the secretogranin II message might be a useful general marker for identifying chronically stimulated neurons.

Intracellular redistribution of neuropeptides and secretory proteins during differentiation of neuronal cell lines

We have demonstrated that the mouse neuroblastoma N18Tg2 cell line and several clones of hybrid ND cells (ND7, ND9 and ND21), derived from the fusion of neonatal rat sensory neurons with that neuroblastoma, show immunostaining to protein gene product 9.5, neuropeptide Y, C-flanking peptide of neuropeptide Y, tyrosine hydroxylase and chromogranins. Synaptophysin could only be detected in ND cells. Immunoreactivities to substance P, calcitonin gene-related peptide, galanin and somatostatin could not be detected in any of these cell lines. After three days of incubation in a differentiation medium, cell processes of various lengths were observed both in neuroblastoma and ND cell cultures. In ND7 cells there was also a redistribution of neuropeptide Y and its C-flanking peptide to the tips of cell processes. The differentiation of cell processes was also accompanied by the appearance of immunostaining to rat chromogranins in their tips. In contrast, synaptophysin expression was found mainly in cell bodies. Neuropeptide Y, its C-flanking peptide and chromogranins have been associated with secretory granules, whereas synaptophysin is a marker for small synaptic-like vesicles. Therefore, our morphological findings further support and expand the view that these markers are primarily associated with different subcellular structures. Moreover, they indicate that the regulated secretory pathway associated with chromogranins is segregated into nerve processes at an early stage of differentiation, when the synaptophysin-associated pathway is not yet mature. ND7 cells thus provide a useful model system for studying changes in the distribution of neuropeptides, cytoskeletal elements and proteins associated with cell secretion during neuronal differentiation.

Immunological characterization of the endoproteases PC1 and PC2 in adrenal chromaffin granules and in the pituitary gland

Specific antisera against synthetic fragment of the endoproteases, PC1 and PC2, were used to characterize these proteins. In one-dimensional immunoblots these antisera labelled components of 85 kDa for PC1 and of 70 kDa for PC2 in purified bovine chromaffin granules and anterior and posterior pituitary of ox and rat. In membranes of bovine chromaffin granules glycoprotein H was identified as the major PC2 immunoreactive spot. A major part of these endoproteases appeared membrane bound.

Sex-Related Differences in Chromogranin A, Chromogranin B and Secretogranin II Gene Expression in Rat Pituitary

Chromogranin A, an acidic secretory protein, is widely distributed throughout diverse endocrine cells and the central and peripheral nervous systems. Chromogranin A is co-stored and co-secreted from secretory vesicles together with the endogenous hormones or neurotransmitters. Recently, two peptides derived from the Chromogranin A precursor have been shown to inhibit secretion from endocrine cells. In the present study, we investigated the regulation of the biosynthesis of Chromogranin A by estrogen in various tissues. In the pituitary, steady-state levels of Chromogranin A mRNA were markedly reduced by 64% in estrogen-treated male rats. At the protein level, a comparable decrease was found. Chromogranin B and secretogranin II, two other secretory proteins co-stored with Chromogranin A, were slightly increased by estrogen. In pituitaries of female rats Chromogranin A mRNA and protein levels were significantly lower than in males. For Chromogranin B on the other hand, a 2-fold increase of mRNA levels was found. Our observations demonstrate that physiologic concentrations of estrogen strongly affect Chromogranin A levels in the pituitary resulting in a sex-related difference in Chromogranin A gene expression. Based on these and previous results demonstrating increased biosynthesis of Chromogranin A by glucocorticoids and calciferol, we suggest that a typical and characteristic feature of the Chromogranin A gene is its regulation by at least three different classes of steroid hormones.