Lysis of the zona pellucida and attachment of embryos to the uterine epithelium in ovariectomized mice treated with oestradiol-17β and progesterone

摘要

Summary. Preimplantation mouse embryos with intact zonae pellucidae were transferred into the uteri of ovariectomized females treated with progesterone, oestradiol-17β plus progesterone, or oestradiol-17β alone; the disappearance of zonae from the uterine lumen was used to determine the presence of 'zona-lytic' activity in situ. Lysis of zonae did not occur in animals treated with progesterone or oestradiol-17β alone. However, lysis did occur when oestradiol-17 β was combined with progesterone; 'zona-lytic' activity reached peak levels within 12 to 24 h, then decreased. Attachment of embryos to the uterine epithelium occurred only in animals treated with oestradiol-17β plus progesterone and was initiated at about the time of peak 'zona-lytic' activity. It is suggested that the chymotrypsin-like enzyme activity present in uterine fluid is involved with the initiation of implantation.