Androgens binding proteins in the cytosol from prepubertal male rat hypothalamus, preoptic area and brain cortex

The cytosol from hypothalamus and preoptic area of prepubertal male rats contains binding proteins for androgens, whereas the cytosol from brain frontal cortex does not. By Scatchard analysis and gel filtration through Sephadex G 200 column, it appeared that there were two classes of binding sites: one with high affinity for androgens and low binding capacity, the other non specific. The dissociation constants at equilibrium ( K D ) were: 7 × 10 −10 M for testosterone and 7 × 10 −11 M for dihydrotestosterone. Specific binding capacities were respectively 6 × 10 −15 and 1.5 × 10 −15 mol/mg of cytosol proteins. The steroid specificity of these binding proteins was checked by competition assays. It appeared that there was no strict specificity neither for testosterone nor for dihydrotestosterone. Taking this fact into account the problem is to know whether these proteins are true receptors and what is their physiological role.