Concanavalin A binding capacity of preimplantation mouse embryos

Mouse embryos collected on Days 2 (2-cell) to 4 (early blastocyst) were treated with pronase to digest the zona pellucida and cultured at 37 degrees C for 3 h. These embryos and untreated Day-5 late blastocysts were exposed to [3H]Con A at 25, 50, 100 or 200 microgram/ml, 4 degrees C for 30 min, washed and counted for radioactivity. Other groups of embryos were incubated with [3H]Con A in the presence of 0.06 M-alpha-methyl-D-mannoside for the detection of non-specific binding. Scatchard plot analysis showed that the total number of Con A molecules bound/embryo increased with development, from 12 X 10(7) in 2-cell embryos to 19 X 10(7) in early blastocysts and to 150 X 10(7) in late blastocysts. The association constants decreased from 3 X 10(6) M-1 in 2-cell embryos to 0.83 X 10(6) M-1 in late blastocysts. The results suggest that the Con A binding sites (probably glycoproteins) on the embryo surface change quantitatively and qualitatively during preimplantation development.