Saccharides localized by fluorescent lectins on trophectoderm and endometrium prior to implantation in pigs, sheep and equids.

Pre-implantation blastocysts together with the corresponding maternal endometrium were obtained from pigs, sheep and equids at known stages of pregnancy. Thin sections of fixed tissue were reacted with FITC-labelled conjugates of lectins specific for alpha-L-fucose, N-acetyl-D-glucosamine, D-galactose, N-acetyl-D-galactosamine and alpha-D-manno- and alpha-D-gluco-pyranosyl residues. The pre-implantation blastocysts of both pig and sheep, throughout the period studied, had a continuous reaction for alpha-L-fucose, which has been suggested to be important in compaction and the expression of SSEA-1 antigen in mouse embryos. Reactivity for N-acetylglucosamine appeared in the blastocysts of both pig and sheep prior to implantation. The staining for fucose and acetylglucosamine was restricted to the apical (maternally apposed) aspect of the trophectoderm. No specific reactivity was observed in horse conceptuses; however, discrete regions of endometrial epithelium stained intensely for N-acetylglucosamine, and may represent 'recognition' sites for the implanting embryo.