In vivo estrogen synthesis by the developing chicken (Gallus gallus) embryo

The concentrations of unconjugated and conjugated estrogens in the allantoic and amniotic fluids of chicken embryos have been followed during incubation. The estrogens estrone, estradiol-17 beta and estradiol-17 alpha were present as their conjugates in the allantoic fluid of female embryos but not of male embryos. No estrogens were detectable in the amniotic fluid of embryos of either sex. Estradiol-17 beta glucuronide, the most abundant estrogen present in female allantoic fluid, was first detectable (159 pg/ml) at Stage 35 of development increasing in concentration to 4210 pg/ml at Stage 45. The concentration of estrogen in allantoic fluid of the partially decapitated embryos at Day 18 (Stage 41) of incubation was not significantly different from that of the intact Stage 41, approximately Day 15 embryo.