Supersensitive gastrin assay using antibodies raised against a cholecystokinin homolog

Abstract

Peptide hormones may occur in particularly low amounts in samples from small animals. Hence, in a rat microdialysis study conventional immunoassays were not sufficiently sensitive to measure gastrin in the dialysis samples. We therefore exploited the observation that antibodies raised against the homologous hormone cholecystokinin (CCK) occasionally bind gastrin peptides with significantly higher affinity than the proper ligand. The immunoassay thus established could detect 1.0 pmol/l in 15 μl microdialysate, which corresponds to 23 attomol gastrin. Such detection limit is five-fold lower than that obtained with the most avid conventional gastrin antibodies. The results may encourage similar approaches for other peptides using homologue-raised antibodies when supersensitivity is required.

Key Words::

• Antibody cooperativity
• cholecystokinin (CCK)
• gastrin
• homology
• peptide hormones
• radioimmunoassay (RIA)

Acknowledgements

The skilful technical and secretarial assistance of Alice von der Lieth and Diana Skovgaard is gratefully acknowledged.

The study was supported by grants from the Danish Biotechnological Program for Peptide Research, the Swedish Society for Medical Research, and the Medical Faculty of Lund University.

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.