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Uptake of oestradiol by the rabbit hypothalamus. Specificity of binding by nuclei in vitro.

ABSTRACT: The binding of [6,7-(3)H]oestradiol-17beta to subcellular fractions of the hypothalamus and the cerebellum of the rabbit was studied in vitro. Uptake of steroid was higher in hypothalamic nuclei than in cerebellar nuclei. Lower binding was observed in other fractions of both tissues. After dialysis of the fractions, hypothalamic nuclei retained a high percentage of oestradiol whereas cerebellar nuclei lost most of the bound steroid. Supernatant fractions of both tissues retained a significant proportion of label after dialysis and after gel filtration on Sephadex G-200. No specific binding was observed in these fractions when subjected to sucrose-density-gradient centrifugation. Purification of nuclei followed by incubation with labelled oestradiol in the absence of the supernatant fraction resulted in loss of binding of steroid by hypothalamic nuclei. Incubation of the purified hypothalamic nuclei with supernatant fraction maintained the binding specificity of hormone retention.

SUBMITTER: Chader GJ

PROVIDER: S-EPMC1179085 | biostudies-other | 1970 Jun

REPOSITORIES: biostudies-other

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Project description:Expression of the primary female sex behaviour, lordosis, in laboratory animals depends on oestrogen-induced expression of progesterone receptor (PgR) within a defined cell group in the ventrolateral portion of the ventromedial nucleus of the hypothalamus (VMH). The minimal latency from oestradiol administration to lordosis is 18 h. During that time, ligand-bound oestrogen receptors (ER), members of a nuclear receptor superfamily, recruit transcriptional coregulators, which induce covalent modifications of histone proteins, thus leading to transcriptional activation or repression of target genes. The present study aimed to investigate the early molecular epigenetic events underlying oestrogen-regulated transcriptional activation of the Pgr gene in the VMH of female mice. Oestradiol (E?) administration induced rapid and transient global histone modifications in the VMH of ovariectomised female mice. Histone H3 N-terminus phosphorylation (H3S10phK14Ac), acetylation (H3Ac) and methylation (H3K4me3) exhibited distinct temporal patterns facilitative to the induction of transcription. A transcriptional repressive (H3K9me3) modification showed a different temporal pattern. Collectively, this should create a permissive environment for the transcriptional activity necessary for lordosis, within 3-6 h after E? treatment. In the VMH, changes in the H3Ac and H3K4me3 levels of histone H3 were also detected at the promoter region of the Pgr gene within the same time window, although they were delayed in the preoptic area. Moreover, examination of histone modifications associated with the promoter of another ER-target gene, oxytocin receptor (Oxtr), revealed gene- and brain-region specific effects of E? treatment. In the VMH of female mice, E? treatment resulted in the recruitment of ER? to the oestrogen-response-elements-containing putative enhancer site of Pgr gene, approximately 200 kb upstream of the transcription start site, although it failed to increase ER? association with the more proximal promoter region. Finally, E? administration led to significant changes in the mRNA expression of several ER coregulators in a brain-region dependent manner. Taken together, these data indicate that, in the hypothalamus and preoptic area of female mice, early responses to E? treatment involve highly specific changes in chromatin structure, dependent on cell group, gene, histone modification studied, promoter/enhancer site and time following E?.

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Uptake of oestradiol by the rabbit hypothalamus. Specificity of binding by nuclei in vitro.

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