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This Article Full Text Full Text (PDF) All Versions of this Article: 68/3/758    most recent biolreprod.102.008698v1 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 Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Glister, C. Articles by Knight, P. G. Search for Related Content PubMed PubMed Citation Articles by Glister, C. Articles by Knight, P. G. Agricola Articles by Glister, C. Articles by Knight, P. G.

Oocyte-Mediated Suppression of Follicle-Stimulating Hormone- and Insulin-Like Growth Factor-Induced Secretion of Steroids and Inhibin-Related Proteins by Bovine Granulosa Cells In Vitro: Possible Role of Transforming Growth Factor ¹

^a School of Animal and Microbial Sciences, University of Reading, Whiteknights, Reading RG6 6AJ, United Kingdom ^b School of Biological and Molecular Sciences, Oxford Brookes University, Oxford OX3 0BP, United Kingdom

The objective was to investigate the potential role of the oocyte in modulating proliferation and basal, FSH-induced and insulin-like growth factor (IGF)-induced secretion of inhibin A (inh A), activin A (act A), follistatin (FS), estradiol (E₂), and progesterone (P₄) by mural bovine granulosa cells. Cells from 4- to 6-mm follicles were cultured in serum-free medium containing insulin and androstenedione, and the effects of ovine FSH and IGF analogue (LR3-IGF-1) were tested alone and in the presence of denuded bovine oocytes (2, 8, or 20 per well). Medium was changed every 48 h, cultures were terminated after 144 h, and viable cell number was determined. Results are based on combined data from four independent cultures and are presented for the last time period only when responses were maximal. Both FSH and IGF increased (P < 0.001) secretion of inh A, act A, FS, E₂, and P₄ and raised cell number. In the absence of FSH or IGF, coculture with oocytes had no effect on any of the measured hormones, although cell number was increased up to 1.8-fold (P < 0.0001). Addition of oocytes to FSH-stimulated cells dose-dependently suppressed (P < 0.0001) inh A (6-fold maximum suppression), act A (5.5-fold), FS (3.6-fold), E₂ (4.6-fold), and P₄ (2.4-fold), with suppression increasing with FSH dose. Likewise, oocytes suppressed (P < 0.001) IGF-induced secretion of inh A, act A, FS, and E₂ (P < 0.05) but enhanced IGF-induced P₄ secretion (1.7-fold; P < 0.05). Given the similarity of these oocyte-mediated actions to those we observed previously following epidermal growth factor (EGF) treatment, we used immunocytochemistry to determine whether bovine oocytes express EGF or transforming growth factor (TGF) . Intense staining with TGF antibody (but not with EGF antibody) was detected in oocytes both before and after coculture. Experiments involving addition of TGF to granulosa cells confirmed that the peptide mimicked the effects of oocytes on cell proliferation and on FSH- and IGF-induced hormone secretion. These experiments indicate that bovine oocytes secrete a factor(s) capable of modulating granulosa cell proliferation and responsiveness to FSH and IGF in terms of steroidogenesis and production of inhibin-related peptides, bovine oocytes express TGF but not EGF, and TGF is a prime candidate for mediating the actions of oocytes on bovine granulosa cells.

¹ This work was supported by the Biotechnology and Biological Sciences Research Council of Great Britain.

² Correspondence. FAX: 44 118 931 0180; e-mail: p.g.knight{at}reading.ac.uk

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