RGD Reference Report - Neurosteroids and female reproduction: estrogen increases 3beta-HSD mRNA and activity in rat hypothalamus. - Rat Genome Database

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Neurosteroids and female reproduction: estrogen increases 3beta-HSD mRNA and activity in rat hypothalamus.

Authors: Soma, KK  Sinchak, K  Lakhter, A  Schlinger, BA  Micevych, PE 
Citation: Soma KK, etal., Endocrinology. 2005 Oct;146(10):4386-90. Epub 2005 Jul 14.
RGD ID: 4889552
Pubmed: PMID:16020475   (View Abstract at PubMed)
PMCID: PMC2877701   (View Article at PubMed Central)
DOI: DOI:10.1210/en.2005-0569   (Journal Full-text)

A central event in mammalian reproduction is the LH surge that induces ovulation and corpus luteum formation. Typically, the LH surge is initiated in ovariectomized rats by sequential treatment with estrogen and progesterone (PROG). The traditional explanation for this paradigm is that estrogen induces PROG receptors (PR) that are activated by exogenous PROG. Recent evidence suggests that whereas exogenous estrogen is necessary, exogenous PROG is not. In ovariectomized-adrenalectomized rats, estrogen treatment increases hypothalamic PROG levels before an LH surge. This estrogen-induced LH surge was blocked by an inhibitor of 3beta-hydroxysteroid dehydrogenase/delta5-delta4 isomerase (3beta-HSD), the proximal enzyme for PROG synthesis. These data indicate that estrogen induces de novo synthesis of PROG from cholesterol in the hypothalamus, which initiates the LH surge. The mechanism(s) by which estrogen up-regulates neuro-PROG is unknown. We investigated whether estrogen increases 1) mRNA levels for several proteins involved in PROG synthesis and/or 2) activity of 3beta-HSD in the hypothalamus. In ovariectomized-adrenalectomized rats, estrogen treatment increased 3beta-HSD mRNA in the hypothalamus, as measured by relative quantitative RT-PCR. The mRNAs for other proteins involved in steroid synthesis (sterol carrier protein 2, steroidogenic acute regulatory protein, and P450 side chain cleavage) were detectable in hypothalamus but not affected by estrogen. In a biochemical assay, estrogen treatment also increased 3beta-HSD activity. These data support the hypothesis that PROG is a neurosteroid, produced locally in the hypothalamus from cholesterol, which functions in the estrogen positive-feedback mechanism driving the LH surge.



Gene Ontology Annotations    Click to see Annotation Detail View

Biological Process

  
Object SymbolSpeciesTermQualifierEvidenceWithNotesSourceOriginal Reference(s)
Hsd3b1Ratresponse to estradiol  IEP  RGD 

Objects Annotated

Genes (Rattus norvegicus)
Hsd3b1  (hydroxy-delta-5-steroid dehydrogenase, 3 beta- and steroid delta-isomerase 1)


Additional Information