Multicomponent system of estrogen-binding proteins in the liver cytosol: Species differences in rats, mice, and guinea pigs

Abstract

Estradiol(E₂)-binding proteins of the liver cytosol of sexually mature female and male rats, mice, guinea pigs, and rabbits were investigated by gel-filtration on Sepharose 6B columns. Components with Stokes' radii (a) of 6–7 and 2.5 nm, forming specific, stable complexes with E₂, were found in the liver of female rats and of male and female mice. Components with values of (a) of 6–7, 2.5, and under 2.0 nm, specifically binding E₂, were discovered in the liver of male rats and male and female guinea pigs. Complexes of E₂ with components with (a) values of 6–7 and under 2.0 nm were relatively stable, whereas the complex of E₂ with the component witha=2.5 nm could dissociate completely in 45 min. It is suggested that at least some of the components of these heterogeneous populations of E₂-binding proteins may participate in the reception of the estrogen signal by the liver.