ABSTRACT
To investigate the participation of intracellular steroid hormone receptors in the sexual transformation process of the Harderian gland, a series of experiments were undertaken in adult golden hamsters. The in-vitro labelling of cytosolic steroid-binding sites with appropriate radioligands revealed the presence of androgen, oestrogen and glucocorticoid but not progestin receptors in the glands from animals of both sexes. The androgen receptor of the female gland was further characterized because it was found to be the predominant intracellular steroid receptor. Studies of binding kinetics using [3H]7α,17α-dimethyl-17β-hydroxy-4-oestren-3-one (DMNT) as ligand, demonstrated a high affinity androgen-binding site with an apparent dissociation constant (Kd) of 0·7 nmol/l and maximal saturation binding capacity of 84·0 ± 3·0 (s.d.) fmol/mg protein. Specificity of the androgen receptor was assessed by displacement analysis; DMNT, 5α-dihydrotestosterone, testosterone and 3α-androstanediol were efficient competitors for the androgen-binding site, while oestradiol-17β, progesterone and dexamethasone exhibited very little, if any, competitive potency. The sedimentation coefficient of the androgen receptor in sucrose density gradients was 8–9 S. These data indicate that the physicochemical characteristics of the androgen receptor from the female gland are similar to those previously described in the male gland. The striking observation of a complete lack of oestrogen-inducible and oestrogen-insensitive progestin receptors in glands cytosol, even after stimulation with cholera toxin, adds further support to the concept that the androgen receptor is the key molecule mediating the hormone-induced sexual transformation of the Harderian gland in this species.
Journal of Endocrinology (1989) 121, 149–156
Heterogeneous Regulation of Steroid Hormone Receptors in the Brain
