Radioimmunoassay of cholecystokinin: comparison of different tracers.
We have compared the binding of cholecystokinin (CCK) antibodies with different sequence-specificities to Bolton-Hunter labeled CCK-33 (125I-BH-CCK-33), CCK-8 (125I-BH-CCK-8) and chloramine-T iodinated gastrin-17 (125I-gastrin-17). The antibody binding was expressed as the final antiserum dilution ('titer') and the effective equilibrium constant of the binding (Ko eff). Antibodies specific for the C- or the N-terminal sequence of CCK-8 all bound well to 125I-BH-CCK-8. In contrast, some of the antibodies directed against the common C-terminus of CCK and gastrin displayed remarkably low binding of 125I-gastrin-17 or 125I-BH-CCK-33, whereas all antisera specific for the N-terminal or midsequence of CCK-33 bound 125I-BH-CCK-33 well. The lower binding of 125I-BH-CCK-33 to some C-terminal antibodies raised against gastrin may be due to a C-terminal conformation of CCK-33 different from that of gastrin. In accord with the high specific radioactivity of 125I-BH-CCK-8, the best sensitivity of CCK radioimmunoassays was obtained with the CCK-8 tracer.
Cantor
P
P
Rehfeld
J F
JF
D000595:Amino Acid Sequence; D000918:Antibody Specificity; D002766:Cholecystokinin / Q000032:analysis* / Q000276:immunology; D003429:Cross Reactions; D000939:Epitopes; D005755:Gastrins / Q000276:immunology; D011863:Radioimmunoassay / Q000592:standards; D012844:Sincalide / Q000276:immunology
D000939:Epitopes; D005755:Gastrins; C013550:gastrin 17; D002766:Cholecystokinin; D012844:Sincalide