Characterization of estradiol receptors in brain cytosols from perinatal ferrets.

Studies were undertaken to characterize the binding of [3H]estradiol ([3H]E2) to blood plasma and to brain cytosols collected from perinatal ferrets of both sexes. A dialysis experiment showed that the binding capacity of plasma for [3H]E2 was low in neonatal ferrets. Saturable, high-affinity binding of [3H]E2 to cytosols prepared from ferret hypothalamus + preoptic area (H + POA), basal temporal lobe, and midbrain + brainstem (sexes pooled) was demonstrated 5 days prior to the date of expected parturition (42-day gestation), as well as on the day of birth and on postnatal days 5 and 10. The binding of E2 to cytosols prepared from H + POA and temporal lobe of newborn ferrets met established criteria for estrogen receptors: (a) it was saturable; (b) it had a high affinity (Kd approximately 10(-10) M); (c) it was apparently macromolecular since it migrated in front of a 4.7 S dansyl-bovine serum albumin marker on sucrose gradients of low ionic strength and eluted in the void volume of Sephadex LH-20 columns; (d) it was apparently proteinaceous since binding was destroyed by preincubation with pronase; and (e) it was steroid-specific. Previous research suggests that perinatal exposure to E2 causes neither behavioral defeminization nor masculinization in the developing ferret. The present findings raise the question of whether estrogens, acting via neural receptors, normally affect brain development in ferrets of either sex.