Long-term suppression of reproductive function by a single dose of gonadotropin-releasing hormone antagonists in a sheep model
Received 14 November 2005; received in revised form 15 February 2006; accepted 15 February 2006. published online 04 September 2006.
Objective
To determine the effect of single long-acting doses of GnRH antagonists on reproductive function in a sheep model.
Design
Observational, model study.
Setting
University-affiliated research unit.
Animal(s)
Nine intact mature Merino sheep in experiment 1 and 12 mature Merino-crossed ewes with the ovary autotransplanted to the neck in experiment 2.
Intervention(s)
Synchronization of estrous cycle either with intravaginal progestins or prostaglandin F2α analogues and treatment with a single dose of GnRH antagonist; evaluation of reproductive activity, plasma sampling, and ovarian ultrasonography.
Main Outcome Measure(s)
Determination of estrus behavior; plasma concentrations of P, FSH, LH, and inhibin A; and number and size of ovarian follicles.
Result(s)
In both experiments, the concentrations of FSH and LH were suppressed when compared with those in control ewes. In experiment 1, the ovulatory cycles were suppressed for ≥55 days in treated sheep. In experiment 2, there were no follicles sized ≥5 mm in treated ewes for 50 days.
Conclusion(s)
The suppression of the development of large follicles for ≥30 days after a single injection of a long-acting GnRH antagonist provides a novel convenient method of pretreatment before COS.
dDivision of Veterinary Basic Sciences, Royal Veterinary College, London, United Kingdom
eSchool of Human Development, Queen Medical Centre, University of Nottingham, Nottingham, Nottinghamshire, United Kingdom
Reprint requests: Antonio Gonzalez-Bulnes, Ph.D., Departamento de Reproduccion Animal, Instituto Nacional de Investigaciones Agrarias, Avenida Puerta de Hierro s/n. 28040-Madrid, Spain (FAX: 00-34-91-347-40-14).
Supported by a grant (G9827407) from the Medical Research Council (United Kingdom). Also supported by a fellowship under the Organisation for Economic Co-operation and Development in the United Kingdom and by the Programa “Ramon y Cajal” in Spain (both, A.G.B.).
ABSTRACT