Biomedical subjects

C E Roselli

Publications and source records attributed to C E Roselli.

At least 55 records · Page 3Linked to original sources

PubMed1992

Estradiol increases the duration of nuclear androgen receptor occupation in the preoptic area of the male rat treated with dihydrotestosterone.

Androgens and estrogens interact in neural tissues to regulate behavioral and neuroendocrine responses. As an initial attempt to identify the cellular level at which these steroids interact, we characterized the time course of nuclear androgen receptor (ARn) occupation in the preoptic area of the hypothalamus (POA) after chronic dihydrotestosterone (DHT) administration and determined whether it was modified by concurrent treatment with estradiol benzoate (EB). We found that ARn levels peaked (47.1 +/- 12.6 fmol/mg DNA) by 12 h after castrated rats were treated with Silastic capsules filled with crystalline DHT and remained significantly elevated for at least an additional 12 h. When EB was injected (2 micrograms/rat) at the same time the DHT capsules were inserted, peak levels of ARn in POA were reached sooner (6 h) and retained longer (48 h). Comparisons with other central and peripheral tissues suggested that this response was unique to the POA. These results suggest that estrogens may modify the response of POA neurons to androgens by altering the duration of ARn occupation.

Animals↗

PubMed1991

Androgen receptor and 5 alpha-reductase activity in the ductuli efferentes and epididymis of adult rhesus macaques.

We measured androgen receptors (AR) and 5 alpha-reductase activity (5 alpha RA) in the ductuli efferentes and epididymides from adult rhesus macaques. Tissue samples were either assayed biochemically for AR or stained immunocytochemically (ICC) with a monoclonal antibody against AR. To estimate 5 alpha RA, tissue microsomes were incubated with [1 alpha,2 alpha-3H]testosterone, and the [3H]dihydrotestosterone formed was quantified. We found significant regional differences in the levels of both 5 alpha RA and AR in the excurrent ducts. In general, both enzyme activity and AR levels were higher in the caput and corpus epididymis than in ductuli efferentes and cauda epididymis. With ICC, positive nuclear AR staining was detected in all epithelial cell types, whereas variable numbers of stromal cells were positively stained. Our data demonstrate that there are segmental differences in the concentrations of 5 alpha RA and AR in epididymis and suggest that there may be regional differences in the regulation of epididymal functions by androgen.

Animals↗

PubMed1991

Synergistic induction of aromatase activity in the rat brain by estradiol and 5 alpha-dihydrotestosterone.

Estrogens are produced locally from androgen precursors by cells within the hypothalamus and preoptic area (POA). The activity of the aromatase enzyme complex responsible for this intracellular conversion is controlled by gonadal steroids. The purpose of this study was to determine: (1) whether estrogen acts together with androgen to regulate aromatase activity (AA) and (2) whether nuclear androgen receptor levels are increased after exposure to combined treatment with estradiol benzoate (EB) and dihydrotestosterone (DHT). Thus, adult male rats were castrated and treated for 1 week with either vehicle (0.1 ml sesame oil, s.c.), EB (2 micrograms/day), testosterone (3-cm Silastic implant), DHT (3-cm Silastic implant) or EB + DHT. These treatments produced hormone levels in the physiologic range. We found that both testosterone and DHT significantly stimulated AA (p less than 0.05 vs. castrated rats). However, testosterone induced AA significantly more than DHT in the POA (p less than 0.05; castrated + testosterone vs. castrated + DHT). EB alone did not affect AA but synergized with DHT to stimulate AA in the POA to levels equivalent with the testosterone-treated group. By comparison, EB alone did not enhance the induction of AA by DHT in the hypothalamus. Combined treatment with EB and DHT had no effect on the concentrations of nuclear androgen receptors in either tissue suggesting that the effect of EB was not mediated through an androgen receptor mechanism. These results suggest that both androgens and estrogens play a physiologic role in the control of estrogen formation in the rat brain. Furthermore, the anatomical specificity that we observed indicates that critical differences in enzyme responsiveness are present in different areas of the brain.

Animals↗

PubMed1991

Sex differences in androgen receptors and aromatase activity in microdissected regions of the rat brain.

Males are generally more responsive than females to the behavioral and neuroendocrine actions of androgens. The present experiments were performed to determine whether these differences may result from sex differences in the number of androgen receptors (AR) in specific brain areas. For this reason, AR binding was compared in both cytosol (ARc) and cell nuclear KCl extracts (ARn) from microdissected brain regions of gonadectomized male and female rats treated with doses of testosterone (T) that produced equivalent physiological circulating androgen levels. In addition, microsomal aromatase activity was measured as a biochemical index of tissue responsiveness to T, since estrogen formation in certain brain areas is regulated by androgen. One week after exogenous T administration, males exhibited significantly higher levels of ARn than females in the bed nucleus of the stria terminalis, periventricular preoptic area, and ventromedial nucleus. Males also had significantly higher aromatase levels in these same areas plus the medial preoptic nucleus and anterior hypothalamus. There were no significant differences in ARn concentrations in eight other nuclei that were examined for significant sex differences in ARc levels observed under these experimental conditions. When ARc levels were compared in untreated gonadectomized male and female rats, males had greater levels of ARc in the bed nucleus of the stria terminalis only, indicating that new receptor synthesis may be responsible for the sex differences observed in T-treated rats. These results suggest that sex differences in neural responsiveness to androgens may be due in part to sex differences in ARn occupation in specific brain regions.

Animals↗

PubMed1990

Regulation of hypothalamic luteinizing hormone-releasing hormone levels by testosterone and estradiol in male rhesus monkeys.

Castration of rhesus monkeys produces hypersecretion of pituitary luteinizing hormone (LH) and a marked reduction in hypothalamic luteinizing hormone-releasing hormone (LH-RH) content. We performed the present study to determine whether treatment with gonadal steroids would reverse the effect of castration by increasing LH-RH content. We found that, when administered in doses that suppressed serum LH, both testosterone (T) and estradiol (E) significantly increased LH-RH in the infundibular nucleus/median eminence. The LH-RH content of 8 other regions, some known to contain LH-RH neurons, was not significantly affected. Thus, gonadal steroids act within a discrete region of the basal hypothalamus to modify LH-RH content. The finding that both T and E were effective in male monkeys supports the hypothesis that aromatization is involved in the negative feedback mechanism.

Animals↗

PubMed1990

Aromatase activity in adult guinea pig brain is androgen dependent.

Androgen metabolism in target tissues constitutes an important step for understanding hormone action. The in situ aromatization of androgen represents one of these metabolic events. We characterized aromatase activity (AA) in a microsomal preparation of brain tissue from adult guinea pigs since earlier reports questioned its presence in neural tissues of this species. Analyses revealed an apparent substrate affinity (approximately 17 nM) that was equivalent in adult males and females. However, adult male brains contained greater quantities of AA than female brains. Specifically, AA in the preoptic area (POA: p less than 0.05) and the medial basal hypothalamus (MBH; p less than 0.01) was greater in males than in females. AA was concentrated in the limbic system and hypothalamus (amygdala greater than POA greater than septum greater than MBH), whereas low levels were consistently measured in cortical tissue. In vitro estrogen formation was significantly lower in POA (p less than 0.05) and MBH (p less than 0.01) after castration. After dihydrotestosterone treatment, AA returned to levels equal to or greater than those observed in intact males. These data indicate that AA does exist in the guinea pig brain and is modulated by androgens through the androgen receptor. The presence of high levels of aromatase activity may suggest a role for locally formed estrogens in brain function in this species.

Androgens↗

PubMed1990

Testosterone regulates progonadotropin-releasing hormone levels in the preoptic area and basal hypothalamus of the male rat.

GnRH is synthesized as part of a larger 92-amino acid prohormone (pro-GnRH). In the present study, we examined the effect of gonadectomy and hormone replacement on the processing of pro-GnRH to GnRH in adult male rats. Immunoreactive levels of pro-GnRH and GnRH in acid extracts of preoptic area (POA) and basal hypothalamus (BH) from intact, castrate, and testosterone (T)-treated castrate males were quantified by RIA. In addition, we used immunocytochemistry to detect pro-GnRH-and GnRH-positive neurons and determine the effects of hormone treatment. Three weeks after castration, the pro-GnRH content of the POA was 2-fold greater than the amount found in intact males. Treatment with T for 1 week lowered the prohormone content to intact levels. Although the pro-GnRH content in the BH was about 50% lower than that in the POA, the BH responded to castration and steroid replacement in a manner identical to the POA. The GnRH content of the BH, but not that of the POA, was significantly reduced after castration and increased by T treatment. On the other hand, the total number of pro-GnRH and GnRH cell bodies visualized by immunocytochemistry was not significantly altered by either treatment. These results show that changes in pro-GnRH content vary in inverse relation to changes in GnRH content and suggest that gonadectomy inhibits the enzymatic processing of precursor, while T treatment promotes it.

Animals↗

PubMed1989

Testosterone regulates aromatase activity in discrete brain areas of male rhesus macaques.

The nonhuman primate brain contains two divergent pathways for testosterone (T) metabolism. Estradiol is biosynthesized from T by aromatization through the first pathway, whereas dihydrotestosterone is produced by the action of 5 alpha-reductase through the second pathway. Previously, we mapped the distribution of these enzyme activities within specific microdissected brain area and determined that aromatase activity (AA), but not 5 alpha-reductase activity (5 alpha RA), was reduced in certain brain areas after castration. In the present study, we measured AA and 5 alpha RA in thirteen brain nuclei and subregions from five castrated and five T-treated castrated male rhesus monkeys to determine whether exogenous androgen treatment could reverse the effects of castration on brain AA. We found that T, administered in a dose that maintained serum levels at 14.2 +/- 1.6 (SEM) ng/ml, suppressed circulating luteinizing hormone (Castrates = 491.9 +/- 86 ng/ml vs. T-treated castrates = 1.8 +/- 0.2 ng/ml), and stimulated AA in specific nuclei including the suprachiasmatic nucleus (n.), periventricular area, ventromedial n., and lateral hypothalamus. T treatment had no significant effect on AA in nine other nuclei or on 5 alpha RA in any brain areas that we studied. These data indicate that AA in diencephalic and limbic structures of the nonhuman primate brain is distributed heterogeneously into androgen-dependent and androgen-independent regions. This distribution is similar to that found in rodents. 5 alpha RA, on the other hand, is more homogeneously distributed than AA in these same brain regions and is not controlled by androgens.

3-Oxo-5-alpha-Steroid 4-Dehydrogenase↗

PubMed1989

Effects of ovariectomy on GnRH mRNA, proGnRH and GnRH levels in the preoptic hypothalamus of the female rat.

Experiments were carried out to investigate the effects of ovariectomy on gonadotropin-releasing hormone (GnRH) messenger RNA (mRNA), proGnRH and GnRH peptide levels in the hypothalamus of female rats. Intact proestrous female rats and female rats, which had been ovariectomized for 2 weeks, were sacrificed at 9.00 h and the preoptic area (POA) and basal hypothalamus (BH) were dissected out and frozen on dry ice. One group of tissues from proestrous control and ovariectomized females were extracted in acetic acid, centrifuged at 13,000 g and the supernatant purified on a C18 column. The purified extract was then radioimmunoassayed for proGnRH, using a specific antiserum to rat proGnRH (ARK-2), and for GnRH using the E1-14 antiserum. Total cellular RNA was isolated from another group of tissues and prepared as Northern blots. Hybridization with 32P-labeled GnRH cRNA was used to detect GnRH mRNA. A third group of proestrous and ovariectomized female rats were perfused, and 50 microns vibratome sections were cut. These were immunostained with proGnRH or GnRH antiserum, followed by in situ hybridization with 35S-labeled GnRH cRNA to detect GnRH mRNA. Based on the histochemical staining, mRNA was colocalized to the cell soma of neurons containing proGnRH and GnRH throughout the POA and BH. Based on the radioimmunoassay, proGnRH levels were 2 times higher in the POA versus the BH, but GnRH levels were 6-7 times higher in the BH. Ovariectomy significantly decreased proGnRH levels in both the POA and BH, while GnRH decreased in the BH. In contrast, quantitative Northern blot analysis demonstrated that ovariectomy had no effect on mRNA levels in the POA and BH. These data indicate that the effects of ovariectomy on proGnRH and GnRH levels are a result of altered translation, posttranslational processing and/or secretion of GnRH.

Animals↗

PubMed1989

Quantitative distribution of nuclear androgen receptors in microdissected areas of the rat brain.

The binding of androgens to specific high-affinity receptor sites in brain tissue is postulated as an initial event in the mechanism of central androgenic action. In an effort to assess the functional capacity of the androgen receptor system in the central nervous system, we measured the concentration of nuclear (ARn) as well as cytosolic androgen receptors (ARc) in 13 microdissected brain samples from intact male and female Sprague-Dawley rats. Tissues from 6 rats were combined for each determination and androgen receptor contents were measured with single-point in vitro assays that used saturating concentrations of high specific activity 3[H]dihydrotestosterone. We found that ARc levels tended to be higher in females than males although the general patterns of distribution were very similar. As expected, ARn concentrations were significantly higher in males than females. The highest concentrations of ARn (greater than 100 fmol/mg DNA) in males were measured in the ventromedial nucleus of the hypothalamus and medial amygdala; intermediate levels (50-100 fmol/mg DNA) were found in arcuate nucleus-median eminence, medial preoptic nucleus, periventricular preoptic area, bed nucleus of the stria terminalis, anterior hypothalamus, periventricular anterior hypothalamus, lateral septum, and parietal cortex, and low levels (less than 50 fmol/mg DNA) were measured in lateral preoptic nucleus and cortical amygdala. With the exception of the periventricular preoptic area (74 +/- 33 fmol/mg DNA), only very low concentrations of ARn were measured in females. These data provide the first quantitative profile of ARn in discrete brain nuclei and subregions of the rat.

Animals↗

PubMed1988

Distribution of androgen receptor in microdissected brain areas of the female baboon (Papio cynocephalus).

We measured androgen receptors in the brain and pituitary of 4 female baboons (Papio cynocephalus) by the in vitro binding of methyltrienolone (R1881) to cytosols from 17 brain subregions as well as anterior and posterior pituitaries. High levels of AR were detected in anterior (22.1 +/- 7.1 (S.E.M.) fmol/mg protein) and posterior pituitary (12.6 +/- 3.3 fmol/mg protein). In brain tissue, the highest androgen receptor levels were found in the infundibular nucleus/median eminence (9.4 +/- 2.3 fmol/mg protein), ventromedial nucleus (6.3 +/- 1.7 fmol/mg protein) and periventricular area (4.9 +/- 1.3 fmol/mg protein). Saturation analysis of anterior pituitary and brain tissue (pool of hypothalamic, preoptic area, amygdala and septum remaining after microdissection of brain nuclei) showed that [3H]R1881 binds to the androgen receptor with high specificity and affinity (Kd = 1.25 x 10(-10) M, 0.45 x 10(-10) M, in anterior pituitary and HPA cytosol, respectively). Serum testosterone levels were low in all animals (0.59 +/- 0.26 ng/ml). With these data we described the quantitative distribution of androgen receptor in the pituitary and in specific brain nuclei in a species of nonhuman primate. The distribution is similar in many respects to that described in the male rat and the data suggest a conservation of androgen receptor distribution across species.

Animals↗

PubMed1988

Testosterone 5 alpha-reductase activity in neural tissue of fetal rhesus macaques.

After development of a 5 alpha-reductase activity (5 alpha-RA) assay based on the capacity of microsomes to convert [3H]testosterone (T) to [3H]dihydrotestosterone (DHT), we analyzed 5 alpha-RA in neural tissues of fetal rhesus macaques at 50, 80 and 150 days of gestation. This method allowed us to collect kinetic data on the properties of the 5 alpha-reductase resident in fetal brain at 150 days of gestation. The Km and Vmax calculated from these data were 4.32 microM and 22.6 nmol.mg protein-1.h-1, respectively. Analyses of 5 alpha-RA in microsomes from the hypothalamic-preoptic area-amygdala (HPA) at dilutions of 1/25 and 1/50 indicated higher enzyme activity with increasing dilution of the microsomes. Measurement of 5 alpha-RA using concentrations of [3H]T which saturated the enzyme in diencephalon (DIEN), brain stem (B.STEM), temporal (TCTX) and frontal cortex (FCTX) of six 50-day old fetuses (3 males and 3 females) revealed no obvious sex differences in 5 alpha-RA, however, a significant difference (P less than 0.05) between tissues was noted. The DIEN and B.STEM contained significantly (P less than 0.05) higher levels 5 alpha-RA than the FCTX while the TCTX contained an intermediate level of activity. Significant increases in 5 alpha-RA were observed in FCTX and TCTX with time of gestation (50, 80 and 150 days). Other tissues, including amygdala, hippocampus, cerebellum, tegmentum and septum also change with fetal age. These data demonstrate the existence of 5 alpha-reductase in the fetal monkey brain. Significant changes in cortical 5 alpha-RA suggest some role for 5 alpha-reductase in development.

3-Oxo-5-alpha-Steroid 4-Dehydrogenase↗

PubMed1988

Perinatal aromatase activity in male and female rats: effect of prenatal alcohol exposure.

Fetal alcohol exposure has been shown to produce long-term feminizing and demasculinizing effects on male rat behaviors which are organizationally dependent upon perinatal androgen levels. Such exposure has previously been shown to suppress the normal surge of testosterone during the critical prenatal period. Since defeminization of male rat behavior is dependent upon estrogen derived from the aromatization of testosterone in brain, brain aromatase activity was measured during the perinatal period in males and females exposed to alcohol beginning on Day 14 of gestation. Aromatase activity was measured in whole hypothalamus of fetuses from Day 16 through 20 of gestation and in the hypothalamic preoptic area and amygdala of animals 6-12 hr postparturition. Hypothalamic aromatase activity was elevated in fetal alcohol exposed males compared to controls on Days 18 and 19 of gestation and on postnatal Day 1. No effect of prenatal alcohol exposure was found in females. A sex effect in aromatase activity in the amygdala was evident on Day 1 when activity was found to be greater in males than females. Overall, these findings indicate that fetal alcohol exposure will elevate regional brain aromatase activity in males, but not females during the perinatal period of neurobehavioral sexual differentiation.

Amygdala↗

PubMed1988

Estrogen and progestin receptors and aromatase activity in rhesus monkey prostate.

We examined nuclear estrogen receptors (ER) and progestin receptors (PR) in the rhesus monkey prostate. Tissues were obtained from six intact males, five untreated castrates, six castrates treated with testosterone (T) for 6 weeks, and four castrates treated with estradiol (E2) for 6 weeks. Samples of the caudal lobe were either assayed biochemically for ER or stained immunocytochemically (ICC) with monoclonal antibodies against the ER or PR. Prostates from untreated castrates had significantly more ER than tissues from intact or T-treated castrates. In E2-treated castrates, ER number increased compared to that in intact and T-treated castrates. With ICC, ER was found only in the nuclei of the fibroblasts and smooth muscle cells of the stroma, not the glandular, ductal, or urethral epithelial cells. Intact and T-treated castrates had a very small number of positive cells, while untreated and E2-treated castrates had a significantly increased number of positive ER cells in the fibromuscular stroma. With ICC, PR was absent in intact or T-treated animals and barely evident in untreated castrates, but was significantly increased in the fibromuscular stroma of E2-treated castrates. The histological preparations indicated there was no stromal hypertrophy in the E2-treated castrates, but the E2 treatment did cause dilation of the glandular acini. Aromatase activity was measured in prostatic microsomes with a radiometric assay. Levels were low (3-30 fmol/h.mg protein) compared to those in brain and placenta, and no differences in activity were seen between castrates and T-treated castrates. Our data demonstrate that androgens can suppress the level of nuclear ER in the rhesus prostate, and that E2 treatment of castrates can induce PR in the same cells as those that contain ER. Thus, under appropriate conditions, estrogens could affect the rhesus prostate through a receptor-mediated pathway.

Animals↗

PubMed1987

Modulation of aromatase activity by testosterone in transplants of fetal rat hypothalamus-preoptic area.

Conversion of androgens to estrogens by neural aromatase appears to be a prerequisite for a variety of effects of androgens on brain function, including sexual differentiation. Activity of aromatase is modulated by its substrate testosterone (T) in adult hypothalamus-preoptic area (HPOA), resulting in significantly higher levels in the male. Perinatal sex differences in activity have also been observed in hypothalamus, POA and/or amygdala. However, it is not known if higher levels in the perinatal male occur in response to circulating androgens, nor whether early exposure to gonadal steroids is necessary to establish either basal levels or the androgen sensitivity of aromatase activity in the adult brain. In order to investigate the influence of early steroid exposure on the development of neural aromatase activity, embryonic day (E)17 fetal HPOA was transplanted onto the choroidal pia overlying the superior colliculus of adult ovariectomized-adrenalectomized (OVX-ADX) Holtzman female hosts. In the first experiment, the effect of androgen exposure on aromatase activity in mature HPOA transplants was determined. Hosts received T-filled silastic capsules or underwent sham surgery 7 weeks after transplantation and were sacrificed 7 days later. Aromatase activity was determined in vitro using the stereospecific production of 3H2O from [1 beta-3H]androstenedione as an index of estrogen formation. Aromatase activity was significantly greater in T-treated HPOA versus controls (P less than 0.005). Activity was not affected by the sex of the donor fetus. In the second experiment, the effect of androgen exposure during the first 6 days following transplantation of E17 HPOA (corresponding to the last gestational week) was determined.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenalectomy↗

PubMed1987

Time-course and steroid specificity of aromatase induction in rat hypothalamus-preoptic area.

We studied the time-course and steroid specificity for aromatase induction in the hypothalamus-preoptic area (HPOA) of the adult male rat. Aromatase activity (AA) was measured in tissue homogenates by using a radiometric assay that quantifies the stereospecific production of 3H2O from [1 beta-3H] androstenedione. We found that by 48 h after administration of testosterone, HPOA AA was significantly (p less than 0.01) greater than control values in castrated rats. In contrast, AA was significantly (p less than 0.01) reduced 12 h after castration, and reached its lowest levels by 4 days after castration. Several other steroids, administered in 3-cm Silastic capsules for 7 days, were tested for their capacity to induce hypothalamic AA. In addition to testosterone, only 5 alpha-dihydrotestosterone and 5 alpha-androstane-3 alpha, 17 beta-diol were effective. Neither the stereoisomers of these compounds nor several other steroids, including estradiol, progesterone, and corticosterone, were active. This profile of activity indicates that the induction of HPOA AA is androgen-specific and, together with the demonstrated time-course of induction, lends further support to the hypothesis that androgens regulate AA through a receptor mechanism and the synthesis of new protein.

Androgens↗

PubMed1987

Regulation of androgen metabolism and luteinizing hormone-releasing hormone content in discrete hypothalamic and limbic areas of male rhesus macaques.

The conversion of androgens to active metabolites by neural tissue is believed to be an essential component in the cellular mechanism of androgen-induced neuroendocrine responses. In this study, we measured the in vitro aromatization and 5 alpha-reduction of androgens in incubations of microdissected brain regions from four intact and five castrated (6 weeks) adult male rhesus monkeys. Individual nuclei were microdissected from 600-microns frozen brain sections and homogenized in a potassium phosphate buffer. Aromatase activity was measured by a radiometric assay that uses the incorporation of tritium from [1 beta-3H]androstenedione into 3H2O as an index of estrogen formation. We estimated 5 alpha-reductase activity by isolating 5 alpha-dihydrotestosterone on two different chromatography systems and measuring the amount of this product formed from [1 alpha,2 alpha-3H]testosterone. We acidified a portion of each homogenate and determined LHRH content by RIA. Between brain nuclei, aromatase activity varied 1500-fold, whereas 5 alpha-reductase activity varied only 3-fold. Both enzyme activities were highest in amygdaloid, medial preoptic, and medial diencephalic nuclei and lowest in the caudate nucleus. Aromatase activities in the supraoptic nucleus, periventricular area, medial preoptic area-anterior hypothalamus, and lateral hypothalamus were significantly (P less than 0.05) lower in castrated males. Castration did not significantly affect 5 alpha-reductase activity, except for an increase in the basolateral amygdala. The highest concentrations of LHRH were in the infundibular nucleus-median eminence and were 30 times greater than amounts measured in preoptic and medial hypothalamic nuclei. The LHRH contents of the infundibular nucleus-median eminence, ventral medial nucleus, and lateral hypothalamus were significantly lower in castrated males (P less than 0.05). In addition, we observed a significant correlation between aromatase activity and LHRH content in the basal hypothalamus of intact males (r = 0.947; P less than 0.05; n = 8), but not in the preoptic-anterior hypothalamus (r = 0.068; P greater than 0.05; n = 10). No correlation was observed between 5 alpha-reductase activity and LHRH content in either area. These data indicate that castration selectively affects androgen metabolism and LHRH content in discrete regions of the brain of male monkeys and suggest that aromatase and 5 alpha-reductase are regulated differentially in the primate brain.

3-Oxo-5-alpha-Steroid 4-Dehydrogenase↗

PubMed1987

The quantitative distribution of cytosolic androgen receptors in microdissected areas of the male rat brain: effects of estrogen treatment.

Estrogen and androgen synergize in the regulation of various neuroendocrine functions. To determine a potential cellular basis of this synergism, we measured androgen receptor (AR) in the cytosol of 16 hypothalamic and limbic nuclei and subregions in castrated male rats and castrated rats treated with estradiol. Androgen receptor was measured by a previously validated in vitro binding assay using the synthetic androgen methyltrienolone [( 3H]R1881). Male Sprague-Dawley rats (250-350 g) were castrated 2 weeks before the implantation of a 2.5-cm Silastic capsule filled with crystalline 17 beta-estradiol. Control rats were sham implanted. Estrogen treatment lasted for 1 week, after which time the animals were killed, their brains were frozen and sectioned, and individual nuclei and subregions were removed by a tissue punch technique. Tissue from six rats were combined for each determination. The highest levels of AR were found in the ventromedial nucleus (16.5 +/- 1.4 fmol/mg protein), medial preoptic area (12.1 +/- 1.4 fmol/mg protein), bed nucleus of the stria terminalis (11.6 +/- 1.4 fmol/mg protein), lateral septum (11.4 +/- 1.4 fmol/mg protein), arcuate nucleus-median eminence (10.9 +/- 2.1 fmol/mg protein), and medial amygdala (10.3 +/- 0.9 fmol/mg protein). Estrogen treatment resulted in significant increases in AR in medial preoptic area (14.8 +/- 0.6 fmol/mg protein; P less than 0.05) and medial amygdala (14.6 +/- 1.2 fmol/mg protein; P less than 0.02). Subsequent studies using block-dissected hypothalamus-preoptic area, anterior pituitary, and prostate revealed significant estrogen-mediated elevations in AR in anterior pituitary cytosol [42.2 +/- 3.0 vs. 26.4 +/- 1.6 fmol/mg protein (control); P less than 0.01], but not in hypothalamus-preoptic area or prostate cytosols. Estrogen treatment had no effect on AR affinity. The binding of [3H]R1881 was specific for AR and was not affected by the addition of radioinert progesterone to the incubation tube. Estimates of AR concentration were similar regardless of whether [3H]R1881 or [3H]dihydrotestosterone was used as the ligand. In this study, we describe the distribution of AR throughout the hypothalamus and limbic areas using biochemical techniques. In addition, we have identified some cellular events that may mediate the synergistic actions of estrogen and androgen on the neuroendocrine system.

Animals↗