Interference of lead with implantation in the mouse: a study of the surface ultrastructure of blastocysts and endometrium.

Implantation chambers, trophoblast and uterine luminal surfaces were examined on days 5 and 6 of pregnancy by electron microscopy in mice with implantation failure due to an intravenous injection of 75 ppm of lead chloride on day 4. Attachment of the trophoblast cells to the surface of the endometrium and closure of the uterine lumina had failed to occur. Uterine epithelial cells in implantation chambers and along the lumina were covered with abundant microvilli. This appearance is similar to that seen in mice in experimental delay of implantation before the oestrogen-induced attachment of the blastocyst has occurred. It may therefore be assumed that lead has in some way interfered with the activity of ovarian steroid hormones on the endometrium. No significant changes were observed in surface ultrastructure of the blastocysts from the lead-treated and control groups.