Characterization of estrogen binding proteins in mouse liver cytosol: Absence of sexual dimorphism

Abstract

Estrogen binding proteins in mouse liver cytosol were characterized by separation on Sephadex G-75 columns, by Scatchard plot analysis, and by hormonal competition studies. A high affinity receptor (56–70 fmol/mg cytosolic protein) with a mol. wt greater than 75,000, K d of 5.7–8.4 × 10 −10M was identified in male and female C3H liver. A second high capacity low affinity (HCLA) binder (200–300 fmol/mg cytosolic protein) with a mol. wt of about 50,000, K d of 1.7–7.2 × 10 −8 was also identified. Following partial purification of the estrogen binders by ammonium sulfate precipitation, Scatchard plot analysis revealed selective removal of HCLA. On Sephadex G-75 filtration, the purification also resulted in selective removal of the 17β-estradiol binding component with a mol. wt of 50,000. Comparison with rat cytosol separations show that the sexual dimorphism in HCLA binding proteins (5 times higher in male than female rat liver) was absent in the mouse liver. These studies document the presence of a specific high affinity estrogen binding protein in mouse liver and indicate that the sexual dimorphism in HCLA proteins is not a universal feature of all rodent species