Inter-relationships among gonadotrophins, reproductive steroids and inhibin in freemartin ewes
| Autor: | Smith Kc, George E Mann, S.E. Long, Knight Pg, Douthwaite Ja, Parkinson Tj |
|---|---|
| Rok vydání: | 2001 |
| Předmět: |
Male
Ovulation endocrine system Embryology medicine.medical_specialty Freemartin medicine.drug_class Reproductive Endocrinology Sheep Diseases Early pregnancy factor Chorionic Gonadotropin Gonadotropin-Releasing Hormone Basal (phylogenetics) Endocrinology Internal medicine medicine Animals Testosterone Progesterone Fetus Sheep biology Estradiol Obstetrics and Gynecology Cell Biology Luteinizing Hormone Freemartinism Kinetics Reproductive Medicine biology.protein Cattle Female Gonadotropin Follicle Stimulating Hormone hormones hormone substitutes and hormone antagonists |
| Zdroj: | Reproduction (Cambridge, England). 122(3) |
| ISSN: | 1470-1626 |
| Popis: | Freemartins are sterile XX/XY chimaeras that occur as a result of placental fusion between male and female fetuses during early pregnancy. Freemartins occur predominantly in cattle, although the prevalence of ovine freemartinism is increasing. In this study, the reproductive endocrinology of ovine freemartins was compared with that of normal sheep. Freemartins had significantly (P < 0.001) higher basal concentrations of LH and FSH than did normal ewes or rams, although the response of LH to GnRH (10 microg) was similar in freemartins, ewes and rams. Resting concentrations of oestradiol were similar in freemartins and ewes and were increased in both after eCG administration. Testosterone concentrations were higher in freemartins than in ewes, but were unresponsive to GnRH or eCG. Administration of 62.5 mg progesterone or 25 lg oestradiol twice a day for 3 days suppressed LH concentrations to baseline values in freemartins, ewes and rams. In ewes, 500 microg oestradiol administered twice a day caused preovulatory surges in LH concentrations, but suppressed LH in freemartins to baseline values. Thus, LH secretion can potentially be regulated in freemartins by gonadal steroids. FSH concentrations in freemartins were not suppressed by doses of inhibin that were effective in ewes and rams. Therefore, freemartins behave in part like castrated animals, as they have high basal concentrations of LH and FSH, which can be stimulated by GnRH and suppressed by gonadal steroids. Conversely, inhibin does not suppress FSH concentrations in freemartins, and freemartins have circulating concentrations of steroids intermediate between those of castrated and normal animals. |
| Databáze: | OpenAIRE |
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