The effect of intrauterine injection of concanavalin A on implantation in mice and rats.

Concanavalin A (Con A) binding sites are present on the surface of blastocysts. When Con A was injected into one uterine horn of the mouse on Day 3 or 5 of pregnancy at 50 or 100 micrograms/horn, or given to the rat on Day 6 or 7 at 200 micrograms/horn, implantation and pregnancy was not affected when compared to the contralateral horn treated with vehicle alone. However, when the same amount of Con A was administered to the mouse on Day 4 or to the rat on Day 5, implantation was significantly decreased, all accompanied by the incidence of deciduomata. The deciduogenicity of Con A is dose-dependent. Also Con A did not affect the development of mouse embryos as a normal number of blastocysts was recovered up to the time of implantation. Thus the inhibition of implantation by Con A could be due to (a) the earlier occurrence of decidual cell response and its subsequent interference with implantation and (b) the involvement of specific sugar groups in implantation.