Inhibition of implantation by intraluminal administration of concanavalin A in mice.

Important characteristics of endometrial implantation sites are the changes of polarity and molecular composition of the cellular surface. For this reason the masking of surface carbohydrates could lead to an inhibition of the recognition by the blastocyst of the endometrial implantation site. Considering the impact of lectins on carbohydrates, we decided to utilize the intraluminal administration (5 microliter) of different concentrations of concanavalin A (15-60 microgram) in pregnant female mice in the preimplantation phase. An inhibition of 100% of implantation wqs obtained with concentrations of 30 and 60 microgram of the lectin administered on days 3 and 4 of the pregnancy (P less than 0.001). Less important effects were observed on administering 15 or 20 microgram of the lectin (73 and 87% of inhibition) and on utilizing the different doses on days 1 and 2 of the pregnancy. Thus, we conclude that the egg must recognize certain molecules of the endometrial surface (alpha-D-mannopyranose and alpha-D-glucopyranose) in order to implant and that the making of these sites potentially constitutes a new contraceptive approach.