Reproduction, Fertility and Development Reproduction, Fertility and Development Society
Vertebrate reproductive science and technology
RESEARCH ARTICLE

Biosynthesis of oestrogen by the early equine embryo proper

James I. Raeside A B , Heather L. Christie A , Rudolf O. Waelchli A and Keith J. Betteridge A

A Department of Biomedical Sciences, Ontario Veterinary College, University of Guelph, Guelph, ON N1G2W1, Canada.

B Corresponding author. Email: jraeside@uoguelph.ca

Reproduction, Fertility and Development 24(8) 1071-1078 http://dx.doi.org/10.1071/RD11275
Submitted: 21 June 2011  Accepted: 7 March 2012   Published: 10 April 2012

Abstract

The embryo proper in early equine pregnancy has recently been shown to have a remarkable capacity for metabolism of oestrogens. High concentrations of oestrogens in yolk-sac fluid could provide substrate for local metabolism in tissues of the embryo proper and this activity could have significance for early development. Due to the high level of oestrogen metabolism in the embryo proper we examined the possibility that it could also biosynthesise oestrogens. Conceptuses were collected in the fourth week of pregnancy (n = 23) and the embryo was separated from extraembryonic tissues for incubation with [3H]androstenedione. Steroids were recovered from media by solid-phase extraction and eluted as unconjugated and conjugated fractions. Profiles of free and sulfoconjugated fractions, as well as the phenolic steroids extracted from them, were obtained by chromatography. Oestrone and oestradiol were seen clearly, indicating oestrogen biosynthesis, and the presence of more polar products, arising from metabolism of the primary oestrogens, gave further evidence that the embryo was capable of oestrogen biosynthesis. Aromatase activity was also demonstrated by detection of tritium loss, as 3H2O, from incubations (n = 3) with [1β-3H]androstenedione. It is suggested that its oestrogen biosynthesis may have significance for the remarkable development of the vasculature in the embryo proper at this stage.

Additional keywords: early pregnancy, oestradiol, oestrone, vasculogenesis.


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