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This Article Full Text Full Text (PDF) All Versions of this Article: 75/4/633    most recent biolreprod.105.048702v1 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 Barrett, D. M.W. Articles by Rawlings, N. C. Search for Related Content PubMed PubMed Citation Articles by Barrett, D. M.W. Articles by Rawlings, N. C. Agricola Articles by Barrett, D. M.W. Articles by Rawlings, N. C.

Suppression of Follicle Wave Emergence in Cyclic Ewes by Supraphysiologic Concentrations of Estradiol-17beta and Induction with a Physiologic Dose of Exogenous Ovine Follicle-Stimulating Hormone¹

Department of Veterinary Biomedical Sciences, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, Saskatchewan, Canada S7N 5B4

ABSTRACT

Follicle waves are preceded by follicle-stimulating hormone (FSH) peaks in ewes. The purpose of the present study was to see whether estradiol implant treatment would block FSH peaks to create a model in which the effect of the timing and mode of FSH peaks could be studied by ovine FSH (oFSH) injection. In Experiment 1, 10 ewes received estradiol-17beta implants on Day 4 after ovulation (Day 0, day of ovulation); five ewes received large implants, and five ewes received small implants. Five control ewes received empty implants. In Experiment 2, 12 ewes received large implants on Day 4. On Day 9, six ewes received oFSH twice, 8 h apart (0.5 µg/kg; s.c.). Implants were left in place for 10 days in both experiments. In both studies, ovarian ultrasonography and blood sampling was done daily. In Experiment 1, estradiol concentrations were significantly higher in ewes with large implants (10.4 ± 0.7 pg/ml) compared with controls (3.9 ± 0.7 pg/ml) and ewes with small implants (5.4 ± 0.7 pg/ml; P < 0.001). A significant reduction was found in mean FSH peak concentration (31%; P < 0.05) and FSH peak amplitude (45%; P < 0.05) in ewes with large implants compared with controls. Mean and basal FSH concentrations were unaffected by the large implants. The large implants halted follicle-wave emergence between Day 0 and 8 after implant insertion. The small follicle pool (2–3 mm in diameter) was unaffected by the large implants. When oFSH was injected into ewes with large implants, a follicle wave emerged 1.5 ± 0.5 days after injection; however, in ewes given saline alone, a follicle wave emerged 4.8 ± 0.8 days after injection (P < 0.01). We concluded that truncation of FSH peaks by estradiol implants prevented follicle-wave emergence, but injection of physiologic concentrations of oFSH reinitiated follicle-wave emergence.

estradiol, follicle-stimulating hormone, follicular development, luteinizing hormone, ovulatory cycle

¹ Supported by the Natural Sciences and Engineering Research Council, Canada (N.C.R.). D.M.W.B., P.M.B., R.D., and K.L.D. were recipients of University of Saskatchewan Graduate Student Scholarships.

² Correspondence: FAX: 306 966 7376; norman.rawlings{at}usask.ca

³ Current address: Department of Biomedical Sciences, Ontario Veterinary College, University of Guelph, Guelph, ON, Canada N1G 2W1.

⁴ Current address: Institut de Génétique et de Biologie Moléculaire et Cellulaire, BP 10142, 67404 Illkirch CEDEX, France.

⁵ Current address: Department of Animal and Poultry Science, College of Agriculture, University of Saskatchewan, Saskatoon, SK, Canada S7N 5A8.

This article has been cited by other articles:

				D. M.W. Barrett, R. Duggavathi, K. L. Davies, P. M. Bartlewski, E. T. Bagu, and N. C. Rawlings Differential Effects of Various Estradiol-17beta Treatments on Follicle-Stimulating Hormone Peaks, Luteinizing Hormone Pulses, Basal Gonadotropin Concentrations, and Antral Follicle and Luteal Development in Cyclic Ewes Biol Reprod, August 1, 2007; 77(2): 252 - 262. [Abstract] [Full Text] [PDF]