Estrogen receptor in chicken oviduct: receptor dissociation kinetics and transformation

Comparison of sex steroid hormone-dependent induction of chick oviduct delta-aminolaevulinic acid dehydratase during primary and secondary stimulation

1. A comparative study on primary and secondary stimulation of oviduct delta-aminolaevulinic acid dehydratase (ALAD) (EC 4.2.1.24) was carried out with oestradiol-17 beta and/or testosterone administration in immature female chickens during 15-day-primary stimulation, 20-day-withdrawal and 15-day-secondary stimulation periods. 2. Compared with primary stimulation in oestrogenized birds, synthesis and degradation rates of oviduct ALAD molecule during secondary stimulation increased 3.4- and 1.8-fold respectively, resulting in a rapid induction of the enzyme. 3. Specific activity of oviduct ALAD in oestradiol-plus-testosterone treated birds became significantly higher than that of oestradiol alone during secondary stimulation, whereas no significant changes were observed during primary stimulation.

A comparison of 11 beta-chloromethylestradiol and tamoxifen aziridine as affinity labeling reagents for estrogen receptors

The tritium-labeled from of 11 beta-chloromethylestradiol was prepared by metal hydride reduction of the 17-keto derivative. Affinity labeling experiments were carried out using [3H] 11 beta-chloromethylestradiol and [3H]tamoxifen aziridine with estrogen receptor from crude, calf uterine cytosol and partially purified (heparin-sepharose chromatography) preparations. Both compounds formed highly stable receptor complexes. Estrogen specific, covalent binding, however, was indicated only for [3H]tamoxifen aziridine. An equilibrium dissociation constant of 2.8 x 10(-10) M was determined for the receptor-[3H] 11 beta-chloromethylestradiol interaction. Measurement of hormone dissociation kinetics at 30 degrees C revealed a slow, single phase dissociation of 11 beta-chloromethylestradiol from the receptor (dissociation rate constant, 1.3 x 10(-3) min-1). This contrasted with the normal biphasic dissociation pattern of estradiol in which the dissociation rate constant for the slower component was 16.7 x 10(-3) min-1. The results indicate that 11 beta-chloromethylestradiol readily converts the estrogen receptor to a high affinity binding form and suggest that the radiolabeled hormone may prove useful for studies of estrogen action.