Influence of endometrial 17 beta-hydroxysteroid dehydrogenase activity on the binding of estradiol to receptors.

Specimens of proliferative and secretory endometrium which differ in the levels of 17 beta-estradiol dehydrogenase activity, were superfused with mixtures of [3H]estradiol ([3H]E2) and [3H]ethynyl estradiol ([3H]EE) in the presence and absence of diethylstilbestrol. Concentrations of labeled E2, EE, and estrone were measured in homogenates and in nuclei isolated from the superfused tissues. The relative proportions of [3H]EE and [3H]E2 bound to nuclear receptor were much higher in secretory than in proliferative endometrium. Since EE binds to the estrogen receptor but is not a substrate for 17 beta-estradiol dehydrogenase, these results demonstrate the influence of metabolism on the binding of E2 to the receptor. The elevated enzymatic activity present in secretory endometrium also accounts for the relatively lower concentration of [3H]E2 and the increased [3H]estrone to [3H]E2 ratio in the superfused tissue.