Steroid receptors in the human prostate. 1. Estradiol - 17beta binding in benign prostatic hypertrophy

Agar gel electrophoresis and ultracentrifugation on continuous sucrose gradients revealed the presence of a 4S estradiol 'receptor' in cytosols of samples of human benign hyperplastic prostate tissue. High affinity (charcoal stability) and saturability (disappearance with excess competitor) binding characteristics of the molecular species concerned facilitated its clear distinction from similarly migrating serum albumin-steroid complexes. Our data, obtained with human serum, purified human albumin and albumin-enriched cytosol strongly suggest that agar gel electrophoresis, when used alone, may lack specificity for the quantification of estrogen 'receptors'. Radioligand binding to these molecules may be obscured by similarly migrating albumin-steroid complexes which fail to dissociate during electrophoresis. We advocate the inclusion of competitor experiments to improve the specificity of the method.