Estrogenic feminization of the LH response to orchidectomy: association with prolonged nuclear XXXX receptor retention and induction of cytoplasmic progestin receptors in brain and pituitary.

@entity251 @entity53 @entity1871 @entity2339 @entity35
A sex difference in the LH rise after gonadectomy is clearly observable in the @entity35 . While male @entity35 respond with an early (10-12 h) increase in LH after orchidectomy, a delayed response (2-3 days) is recorded after ovariectomy. In this study we tested the hypothesis that the delayed response to gonadectomy in the E2-treated males is due to a more prolonged retention of E2 (when compared with the corresponding male feedback signal, @entity251 ) within specific central nuclear receptor sites. Orchidectomized (ORDX) animals implanted with either empty or E2-filled Silastic capsules were sacrificed at 0, 24, 48 and 72 h after ORDX or E2-capsule removal. LH levels in ORDX @entity35 rose several-fold by 24 h, whereas E2-treated, ORDX @entity35 , showed no changes in peripheral LH levels until 72 h after E2-capsule removal. At the time of E2-capsule removal (0 h) large increases in nuclear @entity53 receptor (NER) levels were seen in anterior pituitary, preoptic area, and @entity2339 ( @entity2339 ). Twenty-four hours after E2-capsule removal, NER levels were still high in the 3 areas, and by 48 h NER values had returned to control (ORDX) levels, with the exception of @entity2339 where they were slightly but significantly elevated. The increase in NER, as well as the subsequent decline after E2-capsule removal was paralleled by similar changes in cytosolic @entity1871 receptor (CPR) levels in all three regions. Cytosolic @entity251 levels were not changed by the E2-treatment. The results indicate that the feminized response to orchidectomy observed in E2-implanted males is related to a prolonged retention of the E2-receptor in nuclear sites. Further, they indicate that E2-treatment in males, as is the case in females, can induce a marked increase in progestin receptor levels within specific brain regions as well as in the pituitary. The reduction in NER and CPR levels to castrate values precedes the first detectable increase in peripheral LH levels. In conclusion, the pattern of LH rise after gonadectomy in the @entity35 is dependent upon the steroidal milieu at the time of removal of the gonads.
