Receptor Estrogen Complex in the Nuclear Fraction of the Pituitary and Hypothalamus of Male and Female Immature Rats

Abstract

The specific binding of ³H-estradiol by the nuclear fraction of the hypothalamus and anterior pituitary in male and female immature rats was examined. Anterior pituitaries and hypothalami were incubated in vitro with either ³H-estradiol or ³H-estradiol plus diethylstilbestrol, and the amount of ³H-estradiol in the nuclear fraction was determined. This procedure permits an evaluation of the concentration of specific estrogen binding sites, or the receptor estradiol complex (R · E), present in the nuclear fraction, and the dissociation constant, K^R_d, of the R · E complex. No significant differences were observed in the concentration or K^R_d of R · E when male and female pituitaries were compared. Nuclear R · E complexes in the female hypothalamus were measurable and appeared to be similar to those of the pituitary with respect to K^R_d however, the concentration of R · E was much lower. No nuclear R · E was observed in the male hypothalamus or in a control CNS tissue, female cerebral cortex. It is suggested that testosterone secretion in the developing male rat may alter either the concentration of hypothalamic R · E or its ability to be translocated to the nucleus, while it has little or no effect on the estrogen receptor in the pituitary.