[Characteristics of testosterone-binding cytoplasmic components in the human endometrium and their interaction with...

The existence of macromolecules which specifically bind 3H-testosterone is demonstrated in the soluble fraction of human uterus endometrium. Testosterone receptors of endometrial cytosol are heterogenous and comprise the component with high affinity (Kd--2,9x10(-10) M) and low capacity (concentration of binding sites--0,5 pmoles per mg of protein) and the component with lower affinity and higher capacity (4x10(-9) M and 4 pmoles/mg of protein respectively). Incubation of sliced of endometrium at 37 (but not at 0 degrees) with 3H-testosterone results in the binding of the steroid by chromatin. On the other hand, testosterone-cytoplasmic receptor complex is able to associate with chromatin at 0 degrees. Chromatin did not bind free 3H-testosterone under these conditions. The existence of the receptor for testosterone in endometrial cells promoting its transport into the nucleus and binding with chromatin corroborates the previously shown specific action of testosterone on messenger RNA biogenesis in the uterus. Polyinductor model of regulation of gene expression in higher organisms by steroid hormones is discussed.