Automation of radioimmunoassays for some sex steroids with use of both iodinated and tritiated ligands.

We describe an automated technique for estradiol, progesterone, and testosterone, in which System Olli 3000 pipetting and incubation units are used. After extraction or chromatography, steroids are redissolved in ethanol or buffer, and duplicate aliquots are arranged for radioimmunoassay in 24-tube blocks. Addition of antibodies, tracers (125I or 3H), dextran-coated charcoal for separating free and bound ligands, and removal of a portion of the supernate for counting are all performed by the pipetting instrument. Incubations are at 37 degrees C in the incubation unit, or at 4 degrees C. After counting, steroid concentrations are computed from punch tape records by a Nova 840 computer. The management of assays in 24-tube units, and accurate simultaneous pipetting has reduced experimental error, and because there is no carryover, many different assays can be performed concurrently or in rapid sequence. Various scintillation media are compared.