ESTROGEN RECEPTORS IN RAT ADRENAL-GLAND

Cytosol from the adrenal gland of male and female rats contains a specific binding protein for oestradiol-17β. This protein has all the characteristics of a cytoplasmic oestrogen receptor. It is excluded by Sephadex G-200 gel filtration, has a sedimentation coefficient of 8-9 S by sucrose density gradient centrifugation in low salt and dissociates into a 4 S form by centrifugation in high salt (0.5 M KCl). The binding protein is heat sensitive and oestradiol-17β binding is eliminated by protease and by sulphydryl blocking reagents (2mM p-chloromercuriphenylsulphonate). The bound oestradiol dissociates very slowly at 0°C. The adrenal oestrogen receptors have a very high affinity for oestradiol-17β, but lower affinity for oestradiol-17α and do not bind testosterone, androstene-3,17-dione or corticosterone. Scatchard analysis of the saturation data for oestradiol revealed one class of high affinity binding sites with an apparent equilibrium constant of dissociation KD at 0°C of 5.8 × 10-10M. The number of binding sites was calculated to be 70 fmol/mg cytosol protein. Cytosol fractions from androgen insensitive (tfm) male rats contain oestrogen receptors in amounts very similar to that of the normal littermates. © 1978.