Estradiol-17β and estrone: Studies on their binding to rabbit uterine cytosol and their concentration in plasma

The binding of either 3H-estrogen or estradiol was greater when the incubation was carried on at 4°C than at 24°C, however, the time needed to achieve the maximal binding was greater at 4% than at24dgC.

Abstract

Studies have been carried out on the binding of 3H-estradiol and 3H-estrone to a soluble fraction of rabbit uterus. Dextrancoated charcoal has been used to separate the free and bound moieties at the end of the incubation. The binding of either 3H-estrogen was greater when the incubation was carried on at 4°C than at 24°C. The time needed to achieve the maximal binding, however, was greater at 4°C than at 24dgC. Dextran-coated charcoal removed the free steroid rapidly but the steroid-protein complex underwent minimal dissociation during 30 min of exposure to charcoal. Under the conditions employed, the assay itself had a sensitivity of 5 pg for both steroids. The mean concentrations of estradiol in the plasma of men aged 21–40 was 25.6 ±1.5 (SE) pg/ml, in men aged 70–90 years was 21.8 ±3.2 (SE) pg/ml and in post-menopausal women aged 70–90 years was 45 ± 1.0 (SE) p g/ml. The mean concentrations of estrone in males aged 21–40 years was 30.1 ± 3.8 (SE) pg/ml, in males aged 70–90 years was 43.0 ± 6.5 (SE) pg/ml and in post-menopausal women aged 70–90 years was 22.2 ± 41 (SE) pg/ml.