Two-Site ImmunochemiluminometricAssay of Intact Human Parathyrinin Serum with Use of a Tracer Peptide Purifiedby Reversed-Phase High-PerformanceLiquidChromatography

For this two-site immunochemiluminometric assay of intact human parathyrin (hPTH), the luminescent tracer was syn-thetic hPTH(53-84), conjugated via succinimide linkage to (aminobutyl)ethyl-isoluminol hemisuccinimide (ABEl-H). Purifi-cation of the labeled hPTH(53-84) by reversed-phase high-performance liquid chromatography allowed isolation of the conjugate having the highest incorporation of ABEl-H, 1.6 mol per mole of hPTH(53-84). The solid-phase antibody directed against the N-terminal part of hPTH was immobilized by adsorption onto the polystyrene surface of the assay tube and extracted the intact hPTH and N-terminal fragments. Another antibody against synthetic hPTH(53-84), which bound to the C-terminal part of intact hPTH, was indirectly labeled at its second free binding site with the ABEl-H-labeled hPTH(53-84). The assay has a detection limit of 0.5 pmol/L; i