Estrogen-binding protein in mouse and rat adrenal glands.

Cytosol from rat and mouse adrenal glands has been shown to contain a macromolecule which binds estradiol, but not corticosterone or testosterone. The receptor. estrogen complex has a sedimentation coefficient of 8 S when centrifuged on low salt sucrose gradients. Centrifugation on 0.4 M KC1 gradients results in an 8 S + 4 S transformation. The estrogen-binding entity is, at least partially, a protein since no receptor. estrogen complex can be detected on sucrose gradients after trypsin digestion. On gel chromatography on Sephadex G-200 the 8 S form is eluted in the void volume, whereas the 4 S form is included in the gel matrix and elutes as a protein with M, of 95,000 and a Stokes radius of 41 A. Estradiol binding to the cytosol receptor at 0” is very rapid and the constant KA calculated from Scatchard plots is 2 to 4 x 10y M-‘. With intact adrenals at 25” the hormone is bound and translocated to the nucleus; the subcellular distribution of the receptor.estrogen complex is 85% in the nucleus and 15% in the cytosol. Sucrose gradient analysis of the nuclear KC1 extracts reveals the presence of a receptor. estrogen complex with a sedimentation coefficient of 5 S. No significant differences in the characteristics of the estrogen-binding protein in the two animal species were observed. One adrenal cell contains approximately 1200 estrogen binding sites. The presence of an adrenal estrogenbinding protein with properties similar to those of other steroid receptors in steroid-responsive tissues provides a basis for an understanding of some of the observed effects of sex steroids on the physiology of the adrenal glands.