Steroidogenic enzyme activities in the pre- and post-parturient equine placenta.
Reproduction
; 155(1): 51-59, 2018 01.
Article
en En
| MEDLINE
| ID: mdl-29066529
ABSTRACT
Steroidogenic enzymes in placentas shape steroid hormone profiles in the maternal circulation of each mammalian species. These include 3ß-hydroxysteroid dehydrogenase/Δ5-4 isomerase (3ßHSD) and 17α-hydroxylase/17,20-lyase cytochrome P450 (P450c17) crucial for progesterone and androgen synthesis, respectively, as well as aromatase cytochrome P450 (P450arom) that converts Δ4-androgens to estrogens. 5α-reductase is another important enzyme in equine placentas because 5α-dihydroprogesterone (DHP) sustains pregnancy in the absence of progesterone in the second half of equine pregnancy. DHP and its metabolites decline dramatically days before foaling, but few studies have investigated placental enzyme activity before or at parturition in mares. Thus, key enzyme activities and transcript abundance were investigated in equine placentas at 300 days of gestation (GD300) and post-partum (term). Equine testis was used as a positive control for P450c17 activity. Substrates were incubated with microsomal preparations, together with enzyme inhibitors, and products were measured by liquid chromatography tandem mass spectrometry or radiometric methods (aromatase). Equine placenta expressed high levels of 3ßHSD, 5α-reductase and aromatase, and minimal P450c17 activity at GD300 compared with testis (600-fold higher). At foaling, 3ßHSD and aromatase activities and transcript abundance were unchanged but 5α-reductase (and P450c17) was no longer detectable (P < 0.05) and transcript was decreased. Trilostane inhibited 3ßHSD significantly more in testis than placenta, suggesting possible existence of different 3ßHSD isoforms. Equine placentas have significant capacity for steroid metabolism by 5α-reductase, 3ßHSD and aromatase but little for androgen synthesis lacking P450c17. Declining pre-partum 5α-reduced pregnane concentrations coincide with selective loss of placental 5α-reductase activity and expression at parturition in horses.
Texto completo:
1
Colección:
01-internacional
Base de datos:
MEDLINE
Asunto principal:
Placenta
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Progesterona
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Testículo
/
Esteroide 17-alfa-Hidroxilasa
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17-Hidroxiesteroide Deshidrogenasas
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Andrógenos
Límite:
Animals
/
Pregnancy
Idioma:
En
Revista:
Reproduction
Asunto de la revista:
MEDICINA REPRODUTIVA
Año:
2018
Tipo del documento:
Article
País de afiliación:
Estados Unidos