Enzyme-linked immunoadsorbent assay (ELISA) for calcium-binding protein of human small intestine. A quantitative...

A method for measuring calcium-binding protein (CaBP) in small intestinal biopsies of the human is reported. The assay is performed as a competitive enzyme-linked immunoadsorbent assay (ELISA). Pure CaBP and a cytosol fraction of human jejunum generate competitive displacement curves running in parallel thus demonstrating the antigen specificity of the assay. Non-specific displacement of anti-CaBP antibodies from the solid phase CaBP is negligible as demonstrated by the inability of cytosolic proteins of rat small intestine to produce a detectable response in the assay. The method has a detection limit of 3 ng CaBP (applied in 150 microliter) and a coefficient of variation of 9.8%. The ELISA method is applicable in the study of the role of CaBP in clinical disorders of the small bowel.