Chemiluminescence immunoassay of plasma progesterone, with progesterone-acridinium ester used as the labeled antigen.

This simple solid-phase chemiluminescence immunoassay for measurement of progesterone in extracts of venous plasma has sensitivity and precision similar to that of conventional radioimmunoassay with use of a tritiated antigen. The labeled antigen, 11 alpha-progesteryl-2-succinoyltyramine-4-(10-methyl)-acridini um-9-carboxylate, and a monoclonal antibody to progesterone-11 alpha-succinyl-bovine serum albumin are incubated with a 100-microL aliquot of plasma extract (equivalent to 20 microL of plasma) and 50 microL of a suspension of an IgG fraction of a donkey antiserum to mouse immunoglobulins, covalently attached to cellulose particles. After the antibody-binding reaction (60 min at 4 degrees C), 1 mL of phosphate buffer is added to each tube, the tubes are centrifuged (5 min, 1500 X g), and the supernatant fluid is aspirated. The washing step is repeated and diluted hydrochloric acid (50 mmol/L, 50 microL) is added to the pellet. Luminescence is initiated by oxidation with dilute sodium hydroxide/hydrogen peroxide. The signal is integrated over 10 s. The light yield is inversely proportional to the progesterone concentration in the standard or sample.