Regional changes in the binding of [3H] concanavalin A to mouse blastocysts at implantation: an autoradiographic study.

Implanting and delayed-implanting mouse blastocysts were incubated in vitro with [3H] concanavalin A (Con A), and the distribution of binding on their surfaces was determined by light microscopic autoradiography. The density of binding was uniform on the trophectoderm of delayed-implanting embryos and was not changed on the polar surface of implanting embryos. However, binding was reduced on the proximal mural and distal mural trophectoderm of implanting blastocysts by 36% and 60%, respectively. These results suggest that there is a regional reduction in the density of mannose-like sugars on the surface of mouse blastocysts at the time of attachment and implantation.