The mRNA distribution of chromogranins A and B and secretogranin II was determined in rat brain. In Northern blots the oligonucleotide probes used hybridized with single mRNA species of the expected sizes. With tissue hybridization the mRNA signals for these three proteins were found throughout the brain. However, each of the three messages had a distinct distribution, which was exemplified by the fact that in the various regions either all three proteins, a combination of two or only one of them were apparently synthesized. Significant levels of all three mRNAs were found in several regions of the hippocampus and of the amygdala, in some thalamic nuclei and in the pyriform cortex. On the other hand the subiculum contained only the message for chromogranin A, the granule cell layer of the cerebellum only that for chromogranin B, and in posterior intralaminar thalamic and medial geniculate nuclei and in the nucleus of the solitary tract only secretogranin II mRNA was found. The distinct distributions of mRNAs for the chromogranins in various brain regions support the concept that these proteins are propeptides giving rise to functionally active components.

Distribution of mRNAs for Chromogranins A and B and Secretogranin II in Rat Brain.

Fragments of chromogranin A are present in the urine of patients with carcinoid : development of a specific radioimmunoassay for chromogranin A and its fragments.

Fragments of chromogranin A are present in the urine of patients with carcinoid tumours: development of a specific radioimmunoassay for chromogranin A and its fragments.

Quantitative dot-blot assay for proteins using enhanced chemiluminescence

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.

/pdf/large-variations-in-the-proteolytic-formation-of-a-26ic1xzjyh.pdf

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

Chromogranin A (CgA) and chromogranin B (CgB) are acidic proteins stored in and released from hormone granules in endocrine and neuroendocrine tissue. The chromogranins are postulated to serve as pro-hormones to generate biologically active peptides, which may influence hormonal release and vascular functions or have antibacterial functions. Although N-terminal and C-terminal regions show some species amino acid homology, the chromogranins as a whole display considerable interspecies differences, which prevents their use in comparative studies of biological functions. We present four new radioimmunoassays for the measurement of defined N-terminal regions of CgA and CgB. A new radioimmunoassay for measurement of intact bovine CgA has also been developed. With these assays and two previously published ones, we have compared the cross-reactivity of chromogranins from man, cattle, sheep, goat, pig and horse and compared adrenomedullar content and serum levels of CgA from these species. We have also studied the influence of peptide concentrations and the ionic strength of the mobile phase on molecular weight estimations. Assays with antibodies directed against the N-terminal parts of CgA and CgB showed sufficient interspecies cross-reactivity to allow comparative quantification of the circulating levels in man, cattle, sheep, goat, pig and horse. Assays measuring the intact human or bovine CgA were not suitable for comparative purposes in samples from sheep, goat, pig and horse. Molecular interactions between vasostatin immunoreactive material and intact bovine CgA were demonstrated in gel permeation studies, suggesting that conclusions about the degree of N-terminal processing from elution profiles should be made with caution. Reliable interspecies comparison of chromogranins is difficult, but measurements with region-specific assays may be helpful to study concentrations of chromogranins and chromogranin-related peptides.

/pdf/characterisation-of-n-terminal-chromogranin-a-and-52zkjwmhqt.pdf

Characterisation of N-terminal chromogranin A and chromogranin B in mammals by region-specific radioimmunoassays and chromatographic separation methods

Bovine chromogranin A (CGA) was purified by three steps of column chromatography to a single-band purity in sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The antibody against this preparation was purified by a CGA-coupled Sepharose column, and F(ab')2 and Fab' of the antibody IgG were prepared by enzymatic digestion. An enzyme immunoassay (EIA) system was developed with the F(ab')2 immobilized on polystyrene balls and the Fab' labeled with beta-D-galactosidase. The EIA was able to detect 1 pg of CGA and was three to four orders more sensitive compared with any radioimmunoassay systems hitherto reported. Several neural acidic proteins (dopamine beta-hydroxylase, neuron specific enolase, S-100a protein, and brain-type creatine kinase) showed no cross-reaction. Using this EIA, CGA was detected in all regions of bovine central nervous system. CGA concentrations were within a narrow range, being lowest in the cerebellar white matter and highest in the putamen (17.3 and 78.1 ng/mg protein, respectively). The concentrations were extremely low compared to the concentration in the adrenal medulla (205,000 ng/mg protein). The highly sensitive EIA system should be useful for studies of materials containing very small amounts of CGA.

Highly sensitive enzyme immunoassay for bovine chromogranin A: application for studies of regional distribution in bovine central nervous system.

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Highly sensitive enzyme immunoassay for bovine chromogranin A: application for studies of regional distribution in bovine central nervous system.