Abstract
Bovine eggs matured in vitro and embryos from the 2-cell to expanded blastocyst stages developed in vitro were studied histochemically for the presence of Δ5-3β-hydroxysteroid dehydrogenase (HSD), 17β-HSD, 20α-HSD and 20β-HSD. The activities of Δ5-3β-HSD (dehydroepiandrosterone and pregnenolone as the substrates), 17β-HSD (estradiol-17β and testosterone), 20α-HSD (20α-hydroxyprogesterone) and 20β-HSD (20β-hydroxyprogesterone) were always found in the eggs and embryos 1-cell through blastocyst stages. The activity of Δ5-3β-HSD (17α-hydroxypregnenolone) was observed in the embryos at the stages of 8-cell to blastocyst, but not in the 1-cell eggs and the 2- to 4-cell embryos. From these results, it seems that progestin, such as progesterone, 20α-hydroxyprogesterone and 20β-hydroxyprogesterone, and androgen and estrogen are always getting synthesized in the cultured bovine eggs and embryos throughout the stages of 1-cell to blastocyst, and that 17α-hydroxyprogesterone, one of progestin, is synthesized in the embryos at the stages of 8-cell, morula and blastocyst.
