Localization of aromatase and 5α-reductase to neuronal and non-neuronal cells in the fetal rat hypothalamus

Canick, Jacob A.; Vaccaro, Dennis E.; Livingston, Elizabeth M.; Leeman, Susan E.; Ryan, Kenneth J.; Fox, Thomas D.

doi:10.1016/0006-8993(86)91135-2

Cited by 58 publications

(24 citation statements)

References 21 publications

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“…These results confirm and extend the previous demon stration of aromatase activity in whole brain synaptosomes from birds [9] and rats [11], They also support the notion that, in the brain, aromatase is limited to neurons [21], The intracellular appearance and distribution of neuronal ARO is quite consistent with our previous find ings in the human placenta; utilizing a different polyclon al antihuman placental aromatase antiserum; immunopositivity was found in the rough endoplasmic reticulum throughout the cytoplasm, but not in the nucleus [22].…”

Section: Discussionsupporting

confidence: 81%

Aromatase Immunoreactivity in Axon Terminals of the Vertebrate Brain

et al. 1996

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Intraneuronal production of estradiol from testosterone has been shown to play a pivotal role in gender-specific brain development of most vertebrates, and to participate in numerous functions of the adult central nervous system. Previous biochemical and morphological approaches demonstrated that estrogen synthetase (aromatase) is present in specific limbic and hypothalamic structures. On the other hand, less attention has been paid to revealing its subcellular distribution. The possibility of aromatase presence in axonal processes has been indicated by recent biochemical and morphological observations suggesting new insights for the role of aromatase in neural functions. The objective of the present study was to provide morphological evidence for the subcellular location of aromatase in neurons of different vertebrate species including Japanese quail, rat, monkey, and human. Immunocytochemistry using a purified polyclonal antiserum against human placental aromatase localized immunoreactivity to hypothalamic and limbic cell groups in all of these species. Light and electron microscopic examination of vibratome sections revealed the presence of aromatase immunoreactivity throughout the neuronal perikarya, including dendrites and axonal processes. In each species there were numerous boutons which contained labeled small clear synaptic vesicles. Many of these axon terminals formed synapses with immuno-negative and immuno-positive dendrites and perikarya. This study furnishes the first immunolocalization of aromatase in the brains of two primate species, humans and monkeys. The provision of further evidence for estrogen synthesis in axons and axon terminals may help resolve apparent differences between the measurement of aromatase activity and the lack of aromatase-immunopositive cell bodies in previous studies. The present findings may be coupled with recent evidence regarding the molecular biology and the diversity of functional properties of P450 aromatase to indicate previously unexpected effects of brain aromatase at the synaptic level.

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Section: Discussionsupporting

confidence: 81%

Aromatase Immunoreactivity in Axon Terminals of the Vertebrate Brain

et al. 1996

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“…Previous data show that hypothalamic cultures [26,34] and cerebral cultures [27] from rat fetuses are capable of aromatizing T. However, these studies did not use genderspecific material for their cultures. Therefore, the data presented in this article provides the first evidence that cultured hypothalamic cells develop a sex-specific pattern of T aromatization, which is in agreement with our obser vations using direct homogenate AA assay from neonates and fetuses and reported sex differences in hypothalamic AA during brain development [12,13].…”

Section: Discussionmentioning

confidence: 96%

“…Whereas in the adult avi an and rat brain, androgens are likely to be involved in the regulation of AA [16][17][18][19], no data are available yet to indi cate whether AA is induced or modulated by steroid hor mones during mammalian embryonic and neonatal brain development in males and females [20,21]. However, the developing preoptic aromatase in birds (Japanese quail) is steroid-regulated [22], The aims of our present study are to examine: (1) the gender-specific and brain regional developmental charac teristics of mouse T aromatization in the direct assay of tissues from embryonic day (ED) 17 and neonatal hypo thalamus and cortex, and how these measurements com pare to AA in cultured hypothalamic and cortical cells from ED 15 mouse fetuses, which has been shown pre viously to be a suitable system for studying sexual differ entiation of neurons [23][24][25], Furthermore, we perform aromatase kinetic studies from hypothalamic cells of male and female ED 17 fetuses, neonates, and ED 15 cultures in order to investigate sex differences of aromatase and to compare enzyme binding constants with those described for the adult mouse brain [11], Moreover, because it is still a matter of controversy whether aromatase in the brain is localized primarily in neuronal or non-neuronal cells (such as oligodendrocytes, astroglia-or epithelial cells) [26,27], we investigate the cellular distribution of AA in glial-enriched cell cultures from ED 20 mouse hypothalamus and cortex as well as in ED 15 cultures treated with the neurotoxin kainic acid (KA).…”

Section: Introductionmentioning

confidence: 99%

Sex-Specific Aromatization of Testosterone in Mouse Hypothalamic Neurons

1993

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Conversion of androgens to oestrogens by neural aromatase during brain development appears to be a prerequisite for sexual differentiation of the mammalian central nervous system. In order to investigate the pre- and perinatal patterns of testosterone (T) aromatization in the male and female mouse brain, aromatase activity (AA) was measured in hypothalamic and cerebral homogenates of embryonic day (ED) 17 fetuses and neonates using an in vitro ³H₂O product formation microassay. In addition, AA was examined in gender-specific neuronal cell cultures prepared from ED 15 mouse cerebral hemisphere and hypthalamus at 3 and 6 days in vitro (DIV), and this was compared with enzyme activities in homogenates. The aromatase has also been evaluated in glial-enriched cultures from ED 20 mouse hypothalamus and cortex as well as in ED 15 cultures treated with the neurotoxin kainic acid in order to localize AA to neurons and/or glial cells. Significant sex differencees in AA were observed in hypothalamic tissue homogenates as early as ED 17, becoming even more distinct in neonates, AA being always higher in males compared to females. Similar AA was also found in cells from both sexes from cultured ED 15 hypothalamus after 3 DIV. However, significantly higher AA was observed after 6 DIV in ED 15 male hypothalamic cultures compared to female. ED 20 glial-enriched hypothalamic culutures (purity > 95%) from both brain regions exhibited very low AA after 6 DIV, and no sex differences were found. After treatment of ED 15 hypothalamic cultures with kainic acid, a 70–80% decrease in AA was observed in both sexes compared to non-treated cultures and sex differences were no longer present. Kinetic studies performed on aromatase in male and female hypothalamic cells from ED 15 cultures after 6 DIV, from ED 17 fetuses, and from neonatal homogenates with T as substrate indicate similar T binding affinities in cultures as in embryonic and neonatal homogenates from both genders, with an apparent K_m of ∼ 40 nM. In cortex, from either ED 15 cultures, ED 20 cultures, ED 17 fetuses or neonates, AA was low and sex differences were not observed. Taken together, our results demonstrate: (1) sex differences in hypothalamic AA during pre- and perinatal development in the mouse with a higher capacity for oestrogen formation in male than in female; (2) no sex differences in AA from cortical tissues; (3) no sexual or developmental differences in hypothalamic aromatase T binding affinity; (4) aromatase is neuronal rather than astroglial, and (5) sex differences in AA are consequentially restricted to neurons.

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“…Aromatase has been localized to neuronal cells in the fetal rat hypothalamus [22]. Studies of peptide content [42] and connectivity [28] of cells concentrating E in the rat hy pothalamus have suggested that the majority of E binding cells in this region are neurons.…”

Section: S Ex Differencesmentioning

confidence: 99%

Neuroanatomical Localization of Sex Steroid-Concentrating Cells in the Japanese Quail (Coturnix japonica); Autoradiography with [3H]-Testosterone, [3H]-Estradiol, and [3H]-Dihydrotestosterone

1989

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Steroid autoradiography was undertaken to determine the neuroanatomical loci which might be involved in the activation of steroid-sensitive behaviors in the Japanese quail (Coturnix japonica). Male and female quail were either surgically gonadectomized or photically regressed and implanted with androgen or estrogen to restore normal sexual and courtship behavior. After gonadectomy or implant removal, each quail was injected with 250 µCi of [³H]-testosterone (³H-T), [³H]-estradiol (³H-E₂), or [³H]-dihydrotestosterone (³H-DHT), sacrificed, processed for autoradiography, and the telencephalon, diencephalon, mesencephalon, and rhombencephalon were examined for labelled cells. Following ³H-T or ³H-E₂ injection and autoradiography, labelled cells were found in nucleus septalis lateralis (SL), nucleus preopticus medialis (POM), nucleus paraventricularis (PVN), regio lateralis hypothalami (LHy), nucleus inferior hypothalami (IH), nucleus infundibuli (IN), nucleus intercollicularis (ICo), substantia grisea centralis (GCt), nucleus taeniae (Tn), and in the reticular formation near nucleus motorius nervi trigemini (MV). In addition, following ³H-E2 autoradiography, labelled cells were found around nucleus accumbens (Ac). Following ³H-DHT autoradiography, labelled cells were found only in SL, PVN, Tn, LHy, ICo, and CGt. No labelled cells were found in Ac, POM, IH, IN, or MV even after long exposure times. These results suggest that the nuclei labelled following ³Η-E₂ but not ³H-DHT administration bind exclusively the aromatized metabolites of T. Since quail show a sex difference in male-typical copulatory behavior in response to E₂, labelled cells were counted in POM, LHy, IH, and Tn of male and female quail following ³Η-E₂ injection and autoradiography. No sex differences in the number of labelled cells were found in POM, LHy, or IH. Males were found to have more labelled cells than females in Tn. These results show that sex differences in male-typical copulatory behavior are not due to sex differences in the number of cells binding estrogens in POM. The results reported here constitute the most neuroanatomically extensive report of steroid binding cells to date for a galliform brain, the first comparison in a galliform bird of the distributions of cells labelled following injection of ³H-T, ³H-E2, and ³H-DHT and the first analysis of sex differences in numbers of estrogen-binding cells in four nuclei in the avian brain.

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Localization of aromatase and 5α-reductase to neuronal and non-neuronal cells in the fetal rat hypothalamus

Cited by 58 publications

References 21 publications

Aromatase Immunoreactivity in Axon Terminals of the Vertebrate Brain

Aromatase Immunoreactivity in Axon Terminals of the Vertebrate Brain

Sex-Specific Aromatization of Testosterone in Mouse Hypothalamic Neurons

Neuroanatomical Localization of Sex Steroid-Concentrating Cells in the Japanese Quail (<i>Coturnix japonic</i><i>a</i>); Autoradiography with [<sup>3</sup>H]-Testosterone, [<sup>3</sup>H]-Estradiol, and [<sup>3</sup>H]-Dihydrotestosterone

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