Time trend analysis of plasma unconjugated and sulfoconjugated estrone and 3β-Δ5-steroids in fetal and maternal sheep plasma in relation to spontaneous parturition at term

P. W. Nathanielsz, C. Elsner, D. Magyar, D. Fridshal, A. Freeman, J. E. Buster

Research output: Contribution to journalArticlepeer-review

42 Scopus citations

Abstract

Parturition in the sheep is preceded by a complex series of changes in both fetal and maternal plasma-steroid hormone concentrations. Using the chronically catheterized fetal sheep preparation, we measured unconjugated and sulfoconjugated pregnenolone, 17±-hydroxypregnenolone, dehydroepiandrosterone, and estrone in fetal and maternal plasma over the final 20 days before spontaneous vaginal delivery at term. Where appropriate, third degree polynomial functions were fitted to the changing plasma hormone concentration profile. Fetal and maternal plasma pregnenolone and pregnenolone sulfate both fell from maximum values in the last 4 days of gestation. Fetal and maternal plasma estrone and estrone sulfate concentrations underwent a terminal rise over the last 4 days of gestation that was a mirror image of the fall in plasma pregnenolone and pregnenolone sulfate. Maternal 17±-hydroxypregnenolone rose over the last 4 days of gestation. Fetal 17±-hydroxypregnenolone, maternal and fetal plasma dehydroepiandrosterone sulfate, and fetal plasma dehydroepiandrosterone showed no trend during the period of study. Maternal plasma dehydroepiandrosterone rose over the last 4 days of gestation. These results support the view that increased activity of placental 17±-hydroxylase and 17–20-desmolase is responsible for the conversion of C-21 steroids to estrogens at term. 5-Steroids are present in very high plasma concentrations in fetal sheep plasma and may constitute a more important precursor pool for estrogen biosynthesis than does circulating plasma progesterone.

Original languageEnglish (US)
Pages (from-to)1402-1407
Number of pages6
JournalEndocrinology
Volume110
Issue number4
DOIs
StatePublished - Apr 1982
Externally publishedYes

ASJC Scopus subject areas

  • Endocrinology

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