Previous investigations in our laboratories have shown cycle-dependent variations in human endometrial epithelial glycan expression . Particularly striking alterations were found in the expression and secretion of structures added as late processing modifications: sialoglycans including sialyl Lewis x and a , and keratan sulphate . These oligosaccharides are observed to obey a broadly similar pattern of variation: they increase in abundance after ovulation to reach a maximum in the mid-secretory (implantation) phase. This coincides with the observed increase in abundance of Golgi stacks in early secretory phase glandular epithelium . Thus glycosyl- and sul-fotransferases associated with late processing events may be up-regulated in response to progesterone.
Two questions that emerge from the above observations are whether all nonreducing terminal epithelial glycans share the same pattern of regulation in human endometrium and whether this phenomenon is replicated in other closely related species. In the course of the above studies, we observed that N-acetyl galactosamine (GalNAc)-containing sequences bound by the lectin from Dolichos biflorus (DBA) showed an increase in the secretory phase , but the timing of this behavior was not more precisely defined.