Production of oestrone and oestradiol-17 beta by different regions of the filamentous pig blastocyst

Pig blastocysts aged 14, 15 and 18 days were divided into 15-cm segments representing tissue adjacent to the embryonic disc, an intermediate section and the tip region. Whenever total blastocyst length allowed, the intermediate segment was divided into proximal and distal portions for separate culture. All were rinsed with buffer and were incubated with dehydroepiandrosterone for 3 h. Rinsing buffer and incubation medium were subsequently assayed for concentrations of oestrone and oestradiol-17 beta . The highest production of oestrogen was found in the embryonic disc region. The intermediate regions had the lowest synthetic ability, while the tip region produced more oestrogens than the intermediate regions but less than the disc region. The production of oestrone was higher (P70% as much oestrogen as the disc region. These proportions declined on days 16 and 18 to about 50 and 30% resp. The regional variation in the ability of blastocysts to produce oestrogens may have some influence on the ability of the blastocyst to create within the uterus an adequate microenvironment which permits successful differentiation and placentation..