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This Article Full Text Full Text (PDF) All Versions of this Article: 74/1/202    most recent biolreprod.105.044685v2 biolreprod.105.044685v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal My Folders Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Arreguin-Arevalo, J. A. Articles by Nett, Terry. M. Search for Related Content PubMed PubMed Citation Articles by Arreguin-Arevalo, J. A. Articles by Nett, Terry. M. Agricola Articles by Arreguin-Arevalo, J. A. Articles by Nett, Terry. M.

A Nongenomic Action of Estradiol as the Mechanism Underlying the Acute Suppression of Secretion of Luteinizing Hormone in Ovariectomized Ewes¹

Department of Biomedical Science, Colorado State University, Fort Collins, Colorado 80523

ABSTRACT

The objective of the present study was to determine how rapidly estradiol (E₂) was able to suppress the secretion of LH in ovariectomized (OVX) ewes and to evaluate the ability of conjugated forms of E₂ (E₂ conjugated to BSA [1,3,5(10)-estratrien-3,17ß-diol-6-one-6-carboxymethyloxime:BSA [E₂-BSA] and a novel conjugate, E₂ conjugated to a small peptide [E₂-PEP]) to mimic the actions of E₂ on secretion of LH and FSH. Animals (n = 5–6 per group) were given infusions for 4 h of 50 µg of E₂ or equimolar concentrations of E₂-BSA or E₂-PEP. Treatments with E₂, E₂-BSA, and E₂-PEP each induced an acute suppression of LH secretion (<20 min, P < 0.01). In contrast, E₂, but not E₂-BSA or E₂-PEP, induced the characteristic preovulatory-like surge of LH (at 10 h after priming treatment) and decreased secretion of FSH (at 4 h after priming treatment). In conclusion, the acute inhibition of LH secretion induced by E₂ in OVX ewes supports the concept of a nongenomic action as the mechanism underlying the sudden suppression in secretion of LH. In addition, the fact that conjugated forms of E₂ mimicked only the acute suppression of secretion of LH, without inducing the putative genomic actions on secretion of LH or FSH (i.e., a preovulatory-like surge), suggests that the acute effect of E₂ may be mediated via the plasma membrane.

estradiol, estradiol receptor, follicle-stimulating hormone, luteinizing hormone, pituitary

¹ Supported by the National Research Initiative, competitive grant no. 2005-35203-15376, from the USDA Cooperative State Research, Education, and Extension Service, and by a grant from the Colorado State University Agricultural Experiments Station. The academic program of J.A.A.-A. was supported by the National Council for Science and Technology (CONACYT-Mexico) and the National Institute for Research in Forestry, Agriculture and Livestock (INIFAP-Mexico).

² Correspondence: Terry M. Nett, Animal Reproduction and Biotechnology Laboratory, Department of Biomedical Science, 3801 W. Rampart Rd., Fort Collins, CO 80523-1683. FAX: 970 491 3557; terry.nett{at}colostate.edu

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