A panel of 13 region-specific radioimmunoassays for measurements of human chromogranin B.
BACKGROUND
The primary structure of human chromogranin B (CgB) contains 15 pairs of basic amino acids, which are potential cleavage sites for specific endogenous proteases, but also other sites in the molecule can be subjected to cleavage. Several CgB-related peptides have been identified in tissue extracts.


METHODS
Peptides homologous to defined parts of the human CgB molecule were selected and synthesized. Antibodies were raised and 13 specific radioimmunoassays were developed. Plasma samples from 19 patients with neuroendocrine tumors were collected and measured in all assays.


RESULTS
All region-specific assays measured circulating levels of CgB-related peptides. Only five of the assays measured high concentrations of circulating CgB and two of them correlated with that of intact chromogranin A (CgA).


CONCLUSIONS
The assays presented allow measurements of defined regions of CgB and will thus become important tools for further studies of the processing of CgB. One of the assays merit further investigations as a new marker for neuroendocrine tumors.
Stridsberg
Mats
M
Department of Medical Sciences, Clinical Chemistry, University Hospital, SE-75185 Uppsala, Sweden. mats.stridsberg@akademiska.se
Eriksson
Barbro
B
Oberg
Kjell
K
Janson
Eva Tiensuu
ET
D001665:Binding Sites; D002276:Carcinoid Tumor / Q000097:blood; D002624:Chemistry, Clinical / Q000379:methods*; D053378:Chromogranin B; D002864:Chromogranins / Q000032:analysis* / Q000097:blood*; D004220:Disulfides; D006801:Humans; D018358:Neuroendocrine Tumors / Q000097:blood*; D010190:Pancreatic Neoplasms / Q000097:blood; D010455:Peptides / Q000737:chemistry; D017434:Protein Structure, Tertiary; D011863:Radioimmunoassay
C506134:CHGB protein, human; D053378:Chromogranin B; D002864:Chromogranins; D004220:Disulfides; D010455:Peptides