Simultaneous quantification of oestrogen and progesterone receptors by a ligand binding assay in frozen sections

We describe two modifications of a double-isotope assay for measuring the concentrations of oestrogen receptors and progesterone receptors in tumour cytosols and extracts of frozen tumour sections and endometrial sections. The concentrations of these receptors are derived from single-point/isoelectric focussing assays after incubation of cytosols or section supernatants either with ([125I]vinyl)-nortestosterone and [3H]oestradiol or [125I]oestradiol and [3H]ORG 2058 (16 alpha-ethyl-21-hydroxy-19-nor[6,7(3)H]pregn-4-ene-3,20-dione). The concentrations of the oestrogen and progesterone receptors found in cytosols (r greater than 0.93) and extracts from sections (r greater than 0.8) by dual label assays are highly correlated with those found by single label assays. The method described represents an approach to the determination of oestrogen and progesterone receptors biochemically in an amount of tissue which is comparable to that needed for immunocytochemical procedures.