Androgen Receptors in the Brain: What Are We Measuring?*

Sheridan, Peter J.

doi:10.1210/edrv-4-2-171

Cited by 78 publications

(19 citation statements)

References 40 publications

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“…Activity (expressed as percent of intact, sexually active control males) is reduced to normal level after estrogen treatment. their specific binding sites by E; [28], The fact that an excess of non-aromatizable androgen, DHT, did not displace E: from its nuclear binding sites in the present study argues for specificity, but it does not constitute absolute proof. Since DHT is rapidly metabolized in the dove brain in vitro [12] and in vivo (unpublished data), the competition dose might have been too small to be effective.…”

Section: Occurrence Oj Specific Estrogen Receptorscontrasting

confidence: 61%

Nuclear Uptake of Estrogens in the Male Dove Hypothalamus: Relationship to Aromatase Activity and Behavioral Effects

Steimer

Hutchison

1985

Neuroendocrinology

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The natural estrogen, estradiol-17β, and a synthetic agonist, diethyl stilbestrol (DES), accumulated selectively in cell nuclei of the male dove preoptic area and posterior hypothalamus following intramuscular injection of the corresponding ³H-labelled tracers. Nuclear incorporation of radioactivity was saturable and specific, as shown by the effect of competition doses of unlabelled estrogens. The non-aromatizable androgen, 5α-dihydrotestosterone (DHT), did not compete with estrogens for nuclear binding sites, indicating that cross-reaction with androgen receptors is unlikely. Estradiol uptake was higher in the preoptic area than in the posterior hypothalamus, whereas DES uptake did not differ significantly between these areas. Although both brain areas are likely to contain specific estrogen receptors, only the preoptic area is known to be directly involved in the control of male precopulatory courtship behavior in the dove. Aromatase activity responsible for the local conversion of testosterone to biologically active estradiol-17β, measured in vitro, was also much higher in the preoptic and posterior hypothalamic areas than in adjacent areas of the basal forebrain and hypothalamus. The similarity in localization of aromatase activity and intranuclear uptake of estradiol indicates that the formation of estrogen may occur only within discrete brain areas containing specific estrogen receptors. Intranuclear uptake of DES in the preoptic area, which is half that of estradiol, is correlated with lower effectiveness both in inducing aromatase activity in the preoptic area and in eliciting an estrogen-dependent behavior in castrated males. The effectiveness of estrogens on behavior in the male dove is likely to depend upon characteristics of estrogen receptors in the preoptic area.

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Section: Occurrence Oj Specific Estrogen Receptorscontrasting

confidence: 61%

Nuclear Uptake of Estrogens in the Male Dove Hypothalamus: Relationship to Aromatase Activity and Behavioral Effects

Steimer

Hutchison

1985

Neuroendocrinology

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“…Most probably the de creased binding of DHT seen in vitro in the presence of high amounts of E and P reflects the reported low affinity of these steroids for the AR [11,41] rather than DHTbinding to the E and progestin receptor.…”

Section: Discussionmentioning

confidence: 99%

A Characterization of Estrogen’s Influence on Anterior Pituitary Androgen Receptor: Effect of Bromocriptine Treatment

Rodriguez

1991

Neuroendocrinology

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The action of gonadal steroids are mediated through the binding to specific intracellular receptors. Our recent studies have demonstrated that estrogen (E) treatment will increase the concentration of cytosolic androgen receptor (AR) in the anterior pituitary (AP) gland perhaps reflecting in increased sensitivity of this tissue circulating androgen. However, chronic E treatment also increases AP weight and cell number. Consequently, the following studies were performed to determine the relationship between increases in AP cytosolic AR and increases in AP weight following chronic E treatment. Gonadectomized male and female Fischer 344 (F344) rats were implanted with a 5-mm Silastic capsule of 17β-estradiol. Control animals were sham implanted. Animals were sacrificed at 1 3, 7 and 21 days after the commencement of E treatment and AP glands were weighed and processed for cytosolic AR and nuclear estrogen receptor (ER) content. AR and ER were determined by in vitro binding assays using ³H-dihydrotestosterone and ³H-estradiol, respectively. AP weight increased significantly by 3 days of E treatment in females and by 7 days in males (p < 0.05). However, AP weight of E-treated males was significantly less than females throughout (p < 0.05). Significant increases in AP cytosolic AR content (fmol bound/gland) were detected within 1 day of E treatment to female rats but not until 7 days in male rats. AP cytosolic AR content peaked at 7 days of E treatment in females and 21 days in males. AP cytosolic AR concentration (expressed as per milligram cytosol protein) peaked 3 days after E at which time there were significant E effects in both males and females. AR concentration was not elevated following 21 days of E treatment to female rats. These data suggested that the increases in AP weight following 21 days of E treatment were masking the effects of E on AP cytosolic AR when expressed on a per milligram protein basis. Consequently, we inhibited E-induced AP growth by the simultaneous administration of bromocriptine (BR). BR was administered concurrently with E to female F344 rats by the implantation of a constant release pellet of BR (25 mg/animal/21 days). Animals were sacrificed 21 days following E treatment. Concurrent BR treatment significantly reduced AP weight and plasma prolactin levels following E treatment and increased the concentration but not the content of AR (p < 0.05). These data demonstrate that increases in AR number in the AP as a result of E exposure is not a consequence of AP growth. This suggests that E-induced increases in AR are not related to lactotroph proliferation.

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“…How a change in the ability of androgen receptors to associate tightly with nuclear components would effect an increase in T sensitivity is unclear at present. Alternatively, cytosolic and nuclear androgen receptors may be independently reg ulated in this tissue [25]. Use of HG buffer in the employed procedure for measurement of A Rn precludes simulta neous determination of cytosolic androgen receptors.…”

Section: Discussionmentioning

confidence: 99%

Effects of Bromocriptine and Ectopic Pituitary Transplants on Pituitary and Hypothalamic Nuclear Androgen Receptors in the Male Hamster

et al. 1988

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Nuclear androgen receptors (Arn)were measured in the pituitaries and hypothalami of adult male golden hamsters which had been injected with a long-acting preparation of bromocriptine or had pituitaries from adult females transplanted under the renal capsules. Treatment with bromocriptine markedly reduced pituitary Arn and plasma prolactin levels without altering plasma testosterone levels or hypothalamic Ar _N. Ectopic pituitary transplants did not affect Arn in either the pituitary or the hypothalamus. These findings suggest that normal rates of prolactin synthesis and/or secretion may be required for maintenance of Arn in the pituitary of adult male hamsters.

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Androgen Receptors in the Brain: What Are We Measuring?*

Cited by 78 publications

References 40 publications

Nuclear Uptake of Estrogens in the Male Dove Hypothalamus: Relationship to Aromatase Activity and Behavioral Effects

Nuclear Uptake of Estrogens in the Male Dove Hypothalamus: Relationship to Aromatase Activity and Behavioral Effects

A Characterization of Estrogen’s Influence on Anterior Pituitary Androgen Receptor: Effect of Bromocriptine Treatment

Effects of Bromocriptine and Ectopic Pituitary Transplants on Pituitary and Hypothalamic Nuclear Androgen Receptors in the Male Hamster

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