Expression of 112-kDa estrogen receptor in mouse brain cortex and its autoregulation with age.

The mouse brain cortex expresses ER whose size is larger than uterus and level changes with age and hormonal treatment. Western blot analysis shows the presence of 66 kDa ER in uterus but 112 and 116 kDa ER in the brain. Whereas 116 kDa ER is phosphorylated and predominantly present in nuclei, 112 kDa ER is unphosphorylated and present in both cytosol as well as nuclei. Similar to uterus, the level of ER decreases drastically in the brain cortex of old mice. Hormonal regulation of ER shows age-specific pattern. Ovariectomy reduces the level of ER in adult but increases it significantly in old. While testosterone does not alter the level of ER in either age, estradiol decreases it considerably in old but shows no detectable difference in adult. Our results provide evidence for the expression of a novel form of ER in mouse brain cortex and its regulation by sex steroid hormones in age-specific manner.