[Intracellular distribution of estradiol-binding sites in the hypothalamus of female rats during the estrous cycle].

The content of cytoplasmic and nuclear receptors for estradiol (E2) in the preoptic anterior hypothalamus (PO) and arcuate nucleus-medial eminance (ARC-ME) at varying day time (10, 13, 15 and 18 hours) of each stage of the estrous cycle was examined. The most pronounced changes in the concentrations of estradiol-binding sites in both hypothalamic regions, having high affinity for E2, was seen at the second half of the day of diestrus-2 and proestrus. The association constant values for cytoplasmic and nuclear receptors in PO and ARC-ME were slightly changed during the cycle. It is suggested that the receptors for E2 in both hypothalamic regions participate in regulating the luteinizing hormone preovulatory release.