HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) All Versions of this Article: 72/6/1466    most recent biolreprod.104.038588v1 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 Duggavathi, R. Articles by Rawlings, N.C. Search for Related Content PubMed PubMed Citation Articles by Duggavathi, R. Articles by Rawlings, N.C. Agricola Articles by Duggavathi, R. Articles by Rawlings, N.C.

The Effect of the Manipulation of Follicle-Stimulating Hormone (FSH)-Peak Characteristics on Follicular Wave Dynamics in Sheep: Does an Ovarian-Independent Endogenous Rhythm in FSH Secretion Exist?¹

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

We designed three experiments to investigate the relationship between FSH peaks and ovarian follicular waves and to examine whether an endogenous rhythm of FSH peaks exists in sheep. In experiment 1, anestrous ewes were treated with ovine FSH (oFSH) or vehicle (6 ewes per group) at the expected time of an endogenous FSH peak, to double the FSH-peak amplitude in treated ewes. In experiment 2, anestrous ewes were treated with either oFSH or vehicle (6 ewes per group) at the expected time of two consecutive interpeak nadirs, such that the treated ewes had 5 FSH peaks in the time frame of 3 FSH peaks in control ewes. In experiment 3, to measure FSH concentrations, daily blood samples were collected from 5 cyclic ewes for a control period during the estrous cycle and then for three 17-day periods after ovariectomy. Daily blood samples were collected from another group of 8 ovariectomized ewes that were treated with estradiol-releasing implants and intravaginal progestogen sponges. Doubling the FSH-peak amplitude did not alter the characteristics of the following follicular wave. Increasing the frequency of FSH peaks stimulated the emergence of additional follicular waves, but did not alter the rhythmic occurrence of FSH peaks and follicular wave emergence. Endogenous follicular waves in oFSH-treated ewes emerged and grew in the presence of the growing largest follicle of the induced follicular waves. Finally, based on the observation of serum FSH concentrations in ovariectomized ewes, it appears that there exists an endogenous rhythm for peaks in daily serum FSH concentrations, which is, at least in part, independent of regulation by ovarian follicular growth patterns.

endogenous rhythm, estradiol, follicle, follicle-stimulating hormone, FSH peaks, ovarian follicle, ovary, pituitary, sheep

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

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]

				D. M.W. Barrett, P. M. Bartlewski, R. Duggavathi, K. L. Davies, and N. C. Rawlings 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 Hormone Biol Reprod, October 1, 2006; 75(4): 633 - 641. [Abstract] [Full Text] [PDF]