Occurrence and properties of 17β-oestradiol receptors in rat brain

Abstract

The occurrence and properties of 17beta-estradiol receptors in rat b rain are discussed. The numbers of 17beta-estradiol binding sites were measured separately in cytosols from anterior middle and posterior regions of the hypothalamus of adult rats in various states. The ratio of estrogen-specific high affinity binding site concentration in adult cortex-amygdada-hypothalamus was 1:5:11 in mixed cycling females and 1:3:6 in intact males. In 5-day-old rats the diethylstilbestrol (DES) suppressible binding sites were distributed in roughly equal concentration in both brain areas and at levels similar to those found in adult hypothalamus or amygdala. Equibibrium was reached in less than 5 minutes with uterine or hypothalamic cytosol whereas with pituitary cortex or amygdala more than 10 minutes were required. There was a difference in affinity between pituitary cytosol and cytosol from brain region or uterus. There was no difference in affinity between brain regions or between sexes in the neoates. It may be that the apparently lower affinities for estrone or 17beta-estradiol in the DES suppressible binding system is an artefact due to alpha-fetoprotein-like material in the incubates.