Differential release of estradiol from immobilized estrogen receptors by p-sec-amylphenol: evidence for a functional microheterogeneity of estrogen receptors.

3H-Estradiol-estrogen receptor complexes were adsorbed on a column of heparin-agarose and subjected to a gradient of increasing concentrations of p-sec-amylphenol. At least five peaks of released 3H-estradiol were observed--demonstrating the existence of subsets of heparin-immobilized receptors with different affinities for estradiol. This finding is presented as further evidence for a functional micro-heterogeneity among estrogen receptors. The origin of the observed differences in estrogen receptors and possible relevance of the findings to receptor-mediated responses are discussed.