Cytoplasmic binding of oestradiol-17  in several brain regions, pituitary and uterus of ferrets ovariectomized while in or out of oestrus

Abstract

The reproductive status at the time of ovariectomy had no effect on oestradiol binding. In both groups of ferrets the oestradiol binding capacity of the uterus was approximately 10 times greater than that of the other tissues studied; of these other tissues the highest oestradiol binding capacity was present in the pituitary, followed by hypothalamus, midbrain, amygdala and cerebral cortex. The binding affinity of hypothalamic receptors for oestradiol was the same in ferrets which had been previously ovariectomized while either in oestrus or anoestrus. It is suggested that the occurrence of seasonal oestrus does not depend on changes in the binding capacity or affinity of hypothalamic receptors for oestradiol.

Influences of Photoperiod on Nuclear Androgen Receptor Occupancy in Neuroendocrine Tissues of the Golden Hamster

“…Studies of pho toperiodic mustelids also fail to indicate a correlation between seasonal variations in gonadal hormone concen trations and fluctuations in steroid receptor levels in neuroendocrine tissues. Cytosolic receptors did not vary with day length in ferrets [1], and seasonal differences were not apparent in the anatomical distribution or number of neuronal nuclei labelled by 3H-estradiol in mink [36].…”

Effects of Bromocriptine and Ectopic Pituitary Transplants on Pituitary and Hypothalamic Nuclear Androgen Receptors in the Male Hamster

“…In the seasonally breeding ewe, the autumnal de creases in plasma PRL levels and the susceptibility of LH release to negative estrogen feedback were reported to be accompanied by an increase [14], a decrease [32], or no change [11] in the pituitary estrogen receptors. It has been suggested that these discrepancies may be related to the confounding effects of the general body condition and the secondary estrogen-binding sites [I], In the female ferret, the cytosolic estradiol binding in the pituitary during the seasonal estrus did not differ from values measured during anestrus [5], Perhaps seasonal changes in the steroid regula tion of gonadotropin release are due primarily to alter ations in the susceptibility of hypothalamic catecholaminergic neurons to steroids [27] rather than to pituitary mecha nisms.…”