title: Time-courses of the appearance/disappearance of nuclear androgen + receptor complexes in the brain and adenohypophysis following testosterone administration/withdrawal to castrated male rats: relationships with gonadotropin secretion.
abstract: We characterized the temporal dynamics of brain and pituitary cell nuclear androgen receptor binding and serum androgen and gonadotropin levels associated with the implantation and removal of testosterone (T)-filled Silastic capsules into performed s.c. flank pouches of castrated, awake male rats. These capsules produced serum T levels in the physiologic range. The number of cell nuclear androgen + receptor complexes, as measured in an exchange assay using [3H]R1881, increased 15-fold at 0.5 h after capsule insertion in the HPAS (combined hypothalamus, preoptic area, amygdala and septum) and anterior pituitary gland, but then showed a second progressive rise within the next 8 h. This pattern suggests that T exerts an initial action in the tissues to alter the affinity and/or number of available androgen receptors. There was a lag time of 2-4 h to the first indication of negative feedback suppression of LH secretion. Serum LH levels declined only slightly at 4 h after capsule insertion but continued to fall thereafter, reaching undetectable values by 24 h. In contrast, serum FSH levels declined only slightly after 24 h of T exposure. After removal of the T capsules, serum T levels declined to castrate values within 2 h at which time the level of androgen + receptor complexes had fallen to 60% in the brain and pituitary. Serum LH and FSH concentrations were unchanged at 2 h after capsule removal, but rose significantly within the next 2 h. The data indicate that the occupation of androgen receptors rapidly changes in response to variations in circulating T in a fashion that implicates their involvement in the expression of this steroid's negative feedback actions on gonadotropin secretion.
authors.affiliation: Laboratory of Neuroendocrinology, Rockefeller University, New York, NY 10021.
authors.forename: L C
authors.initials: LC
authors.lastname: Krey
authors.forename: M Y
authors.initials: MY
authors.lastname: McGinnis
mesh_terms: D000728:Androgens / Q000032:analysis*; D000818:Animals; D001923:Brain Chemistry / Q000187:drug effects*; D002467:Cell Nucleus / Q000032:analysis; D005640:Follicle Stimulating Hormone / Q000378:metabolism*; D007986:Luteinizing Hormone / Q000378:metabolism*; D008297:Male; D009919:Orchiectomy; D010903:Pituitary Gland, Anterior / Q000032:analysis*; D051381:Rats; D011919:Rats, Inbred Strains; D011944:Receptors, Androgen / Q000032:analysis*; D011960:Receptors, Estrogen / Q000032:analysis; D013739:Testosterone / Q000097:blood / Q000494:pharmacology*
chemical_list: D000728:Androgens; D011944:Receptors, Androgen; D011960:Receptors, Estrogen; D013739:Testosterone; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone