A COMPARISON OF THE COMPETITIVE PROTEIN-BINDING ASSAY AND RADIOIMMUNOASSAY FOR PLASMA PROGESTERONE DURING THE NORMAL MENSTRUAL CYCLE

Abstract

SUMMARY A protein-binding assay for plasma progesterone using 2% aqueous chick plasma as the binding solution is described. Details of specifications for petroleum spirit to extract the plasma are given, no chromatographic step being employed. Bound and free steroid are separated by Florisil. The system will assay plasma progesterone at a concentration of 2·0 ng/ml; other reliability data are evaluated. One technician can assay 12 duplicate plasma samples per day. The radioimmunoassay method has utilized two antisera, the first, antiprogesterone-20-0-carboxymethyl-oxime—bovine serum albumin at a dilution of 1 in 3000, the second, anti-progesterone-11-succinyl—bovine serum albumin at a dilution of 1 in 10000. Bound and free steroid are separated by dextran—charcoal suspension. The system will assay plasma progesterone at a concentration of 1·0 ng/ml. One technician can assay 24 duplicate plasma samples per day. There is a good correlation between results obtained by both competitive protein-binding (CPB) and radioimmunoassay (RIA) methods. Both methods have a place in estimating the large numbers of serial samples required in the study of physiological situations, although the RIA method will probably supersede the CPB because of its robustness and greater output.