Steroidogenic enzyme activities in the pre- and post-parturient equine placenta

Erin L. Legacki, C. Jo Corbin, Barry A. Ball, Kirsten E. Scoggin, Scott D Stanley, Alan J Conley

Research output: Contribution to journalArticle

9 Citations (Scopus)

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 17a-hydroxylase/17,20-lyase cytochrome P450 (P450c17) crucial for progesterone and androgen synthesis, respectively, as well as aromatase cytochrome P450 (P450arom) that converts 4-androgens to estrogens. 5a-reductase is another important enzyme in equine placentas because 5a-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, 5a-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 5a-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 5a-reductase, 3ßHSD and aromatase but little for androgen synthesis lacking P450c17. Declining pre-partum 5a-reduced pregnane concentrations coincide with selective loss of placental 5a-reductase activity and expression at parturition in horses.

Original languageEnglish (US)
Pages (from-to)51-59
Number of pages9
JournalReproduction
Volume155
Issue number1
DOIs
StatePublished - Jan 1 2018

Fingerprint

3-Hydroxysteroid Dehydrogenases
Isomerases
Placenta
Horses
Aromatase
Parturition
Oxidoreductases
Enzymes
20-alpha-Dihydroprogesterone
Androgens
Testis
Pregnancy
Cytochrome P-450 Enzyme System
Progesterone
Steroids
Steroid 17-alpha-Hydroxylase
Pregnanes
Enzyme Inhibitors
Tandem Mass Spectrometry
Mixed Function Oxygenases

ASJC Scopus subject areas

  • Reproductive Medicine
  • Embryology
  • Endocrinology
  • Obstetrics and Gynecology
  • Cell Biology

Cite this

Steroidogenic enzyme activities in the pre- and post-parturient equine placenta. / Legacki, Erin L.; Jo Corbin, C.; Ball, Barry A.; Scoggin, Kirsten E.; Stanley, Scott D; Conley, Alan J.

In: Reproduction, Vol. 155, No. 1, 01.01.2018, p. 51-59.

Research output: Contribution to journalArticle

Legacki, Erin L. ; Jo Corbin, C. ; Ball, Barry A. ; Scoggin, Kirsten E. ; Stanley, Scott D ; Conley, Alan J. / Steroidogenic enzyme activities in the pre- and post-parturient equine placenta. In: Reproduction. 2018 ; Vol. 155, No. 1. pp. 51-59.
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