A double-antibody radioimmunoassay for serum progesterone using progesterone-3-(O-carboxymethyl) oximino-[125I]-iodo-histamine as radioligand.

A reliable, convenient and economical radioimmunoassay (RIA) for serum progesterone has been established and tested. This procedure employs diethyl ether extraction followed by RIA utilizing rabbit anti-11 alpha-hydroxyprogesterone 11-hemisuccinyl-bovine serum albumin (progesterone-11 alpha-BSA) serum, progresterone-3-(O-carboxymethyl) oximino-125I]-iodohistamine (progesterone-3-125I]) as radioligand and goat anti-rabbit gamma globulin as second antibody. In conjunction with antiprogesterone-11 alpha-BSA serum, the overall assay specificity of the progesterone-3-125I] RIA is similar to that of the 3H]-progesterone method using dextran-coated charcoal. The results of serum progesterone measurements during the menstrual cycle obtained by the progesterone-3-125I] RIA appear comparable to those of 3H]-progesterone assays which employ similar anti-progesterone-11 alpha-BSA sera. The progesterone-3-125I] double-antibody RIA, however, is more convenient and less expensive than the 3H]-progesterone RIA method.