Increase in concanavalin A binding sites in mouse blastocysts during implantation.

The number of concanavalin A (Con A) binding sites were determined in mouse blastocysts before and during implantation. In intact pregnant mice (Day 1 = day of finding vaginal plug), the Con A binding sites per blastocyst were increased from 169 million on Day 4 morning to 1160 million on Day 5 morning when implantation was under way. In pregnant mice ovariectomized on Day 3 and treated daily with 1 mg progesterone, the Con A binding sites per blastocyst on Day 9 (inactive) were 363 million; if the mice had received an additional injection of estradiol 24 hours earlier to induce implantation, the Con A binding sites were increased to 1211 millions. Thus, a more than twofold increase in the Con A binding sites occurs in the mouse blastocyst during implantation.