Steroids in the establishment and maintenance of pregnancy and at parturition in the mare
| Autor: | Barry A. Ball, Alan J Conley |
|---|---|
| Rok vydání: | 2019 |
| Předmět: |
0301 basic medicine
Embryology endocrine system Physiology Placenta Clinical Sciences Dehydroepiandrosterone Luteal phase Biology Andrology Paediatrics and Reproductive Medicine 03 medical and health sciences 0302 clinical medicine Endocrinology Pregnancy Dehydroepiandrosterone secretion Progesterone receptor medicine Animals Horses Equine chorionic gonadotropin Obstetrics & Reproductive Medicine reproductive and urinary physiology 030219 obstetrics & reproductive medicine Animal Parturition Obstetrics and Gynecology Cell Biology 030104 developmental biology Reproductive Medicine Pregnenolone Pregnancy Animal Gestation Steroids Female medicine.drug Hormone |
| Zdroj: | Reproduction (Cambridge, England), vol 158, iss 6 |
| Popis: | Historically, studies on the endocrinology of pregnancy and parturition in horses have made major contributions of relevance to mammals in general. Recent use of liquid chromatography mass spectrometry, measuring multiple steroid hormones simultaneously in blood, foetal and placental tissues throughout normal gestation, and in mares with experimentally induced placentitis, has advanced our current understanding of many of the unusual strategies seen during gestation and at foaling. This includes the stimulation of luteal steroidogeneisis by equine chorionic gonadotropin (eCG) from the endometrial cups, resulting in additional androgen and oestrogen secretion. Progesterone declines as the endometrial cups and eCG disappears, replaced by 5α-dihydroprogesterone (DHP), a potent equine progesterone receptor (PR) agonist, as the chorioallantoic placenta develops. Placental steroidogenesis thereafter is influenced by foetal pregnenolone and dehydroepiandrosterone secretion, providing substrate for 5α-pregnane and oestrogen synthesis, an unusual example of a ‘foeto-placental unit’. Foetal gonadal dehydroepiandrosterone fuels placental oestrone sulphate secretion, peaking at higher concentrations in mares than any other species known, declining steadily thereafter to term. Additional 5α-reduced (DHP) metabolites increase from mid-gestation to peak concentrations 3–5 days before foaling, declining prepartum, most likely as a result of selective loss of placental SRD5A1 (5α-reductase) expression and activity. Similar changes occur in mares with experimentally induced placentitis, which is also associated with a decreased ratio of equine PR-B:PR-A in myometrium, suggesting that progestin withdrawal is both systemic (pregnanes) and local (receptor-dependent) in mares. In addition, some steroids detected during equine pregnancy by immuno-assay are not detected by mass spectrometry, further illustrating the immense value of this technology. |
| Databáze: | OpenAIRE |
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