The binding of estrogen to liver nuclei from Japanese quail

Specific binding sites for estrogen were characterized in liver nuclei from adult Japanese quail. A single class of high-affinity binding sites (KD = 2 X 10(-10) M) was revealed by saturation analysis using an exchange assay. Estradiol (E2), estrone, and estriol competed effectively with [3H]E2 for the nuclear binding sites but progesterone and testosterone were ineffective. The concentration of sites was 0.15 +/- 0.05 pmol/mg DNA (mean +/- 1 SD) in sexually immature females and 0.47 +/- 0.11 pmol/mg DNA in layers. Nuclear estrogen binding sites were not detected in liver nuclei from male Japanese quail. However, after treatment of male birds with E2 there was a dose-dependent accumulation of binding sites. The maximum number of occupied sites was obtained with 50 ng E2/g body wt and equaled that found in laying females. The estrogen binding sites were retained in nuclei of estrogen-treated male quail with a T1/2 of 2.5 hr. Thus, an estrogen binding component was characterized in quail liver nuclei that had features consistent with an estrogen receptor, including high affinity, limited capacity, structural specificity, tissue specificity, nuclear translocation, and nuclear retention.