Effects of chlorpromazine on the inhibition and artifactual elevation of [3H]estradiol binding to estrogen receptors in rat uterine cytosol

Chlorpromazine acts to inhibit the specific binding of estradiol in rat uterine cytosol in vitro at concentrations between 0.1 and 0.75 mM. However, at higher concentrations (1.0-2.0 mM) it causes an apparent increase in binding that is due to free labeled estradiol in the assay buffer which is not adsorbed by the charcoal-dextran. This artifactual elevation can lead to misinterpretations of drug-induced potentiation of receptor sites.