Detection of glycosylated proteins in rabbit oviductal isthmus and uterine endometrium during early embryo development.

In this study, lectin histochemistry was performed on paraffin sections to compare carbohydrate expression of oviductal isthmus and uterine endometrium in rabbits during early embryo development. Rabbit embryos are surrounded not only by the zona pellucida but also by tubal secretion-derived mucinous coat material, the mucin coat. Twenty sexually mature females were euthanized at 0 (pre-ovulatory group) and 24, 72 and 96 h after insemination (pseudopregnancy group). The following lectin-binding agents were used: Arachis hypogaea, Peanut (PNA) to label galactosyl (β-1,3)N- acetyl-galactosamine, Dolichos biflorus Agglutinin (DBA) to label galactosyl (β-1,4)N- acetyl-galactosamine, Lens curinaris (LCA) to label α--mannose, α-d-glucose and Pisum sativum agglutinin (PSA) to label α-d-mannose, α-d-glucose. Blood was collected by cardiac puncture, and direct enzyme immunoassay technique was used to measure progesterone concentration. A significant increase in total plasma progesterone concentrations was detected at 96 h post-ovulation when compared with 0, 24 and 72 h post-ovulation (2.9 ± 0.5 vs 0.5 ± 0.15, 1.6 ± 0.5 and 1.5 ± 0.4 ng/ml, at 96 h vs 0, 24 and 72 h post-ovulation, respectively). No differences between pre-ovulatory and pseudopregnant females were observed for glycoprotein localization in isthmus. In contrast, in the endometrium, differences in the glycoprotein detection between pre-ovulatory and pseudopregnant stages were detected. PNA to label galactosyl (β-1,3)N- acetyl-galactosamine was not detected at the pre-ovulatory stage, but its presence was detected at 24 h after ovulation. Both PSA and LCA to label α-d-mannose, α-d-glucose were only detected at 72 h after ovulation. DBA detection was similar for all stages of the reproductive cycle. Therefore, N-acetyl-galactosamine secreted from isthmus could be involved in the formation of the embryonic mucin coat. d-galactose (PNA), d-glucose and d-mannose (PSA and LCA) might be crucial for the implantation period.