Cytoplasmic and nuclear binding of estradiol in the brain and pituitary of old female rats.

The subcellular distribution of estradiol following the in vivo administration of 3H-estradiol, cytosol and nuclear estrogen receptor after in vitro incubation with 3H-estradiol were studied in young adult female rats (3-6 months old) and old female rats (over 18 months old). After intravenous injection of 3H-estradiol, with or without deithylstilbestrol pretreatment, significantly higher cytosol uptake of estradiol in the pituitary, dorsal hypothalamus and corticomedial amygdala (AMYG) with concomitant significantly lower nuclear uptake in the preoptic area (POA) and basomedial hypothalamus (BMH) and a tendency of lower nuclear uptake in AMYG and pituitary of old noncyclic (NC) rats as compared with young adult female rats were observed. The uterus of NC rats had a low ratio of milligrams of protein per milligram wet weight as compared with young rats and the nuclear binding 1 h after the injection was significantly lower than that of young rats when the value was expressed as disintegrations per minute per milligram weight but not when expressed as disintegrations per minute per milligram protein. Assays of cytosol and nuclear estrogen receptor after in vitro incubation with 3H-estradiol revealed that old prolonged vaginal cornification (PVC) rats did not react estradiol priming with increased nuclear receptors in the pooled brain tissues of AMYG, POA and BMH, anterior pituitary and uterus. These results indicate that there seems to be an impaired translocation of estradiol from cytosol to nucleus in old PVC rats.