[Cytosolic and nuclear estradiol receptors in the fetal guinea pig uterus].

After administration in situ of 3H-estradiol (8 X 10(-10) moles) to Guinea Pig fetuses (48-58 days of gestation) the presence of specific estradiol receptors in the cytosol and in the nuclear extracts of the fetal uterus has been demonstrated. The presence of these estradiol receptors was confirmed after incubation of the same fetal tissues with 3H-estradiol (8 X 10(-8) M). Estradiol has a significant competitive effect on the 3H-estradiol-complex; estrone and estriol also have an effect but less intense. Testosterone, cortisol, aldosterone have no effect. By ultracentrifugation in sucrose density gradient of the cytosol fraction a component with a sedimentation coefficient of 8.5-9 S is observed. The dissociation constant of the 3H-estradiol receptor has a high affinity (KD = 4 X 10(-10) M).