Glycoproteins in rabbit uterus during implantation. Differential localization visualized using 3H-N-acetyl-glucosamine labelling and FITC-conjugated lectins.

The synthesis of glycoproteins in rabbit uterine epithelium during the late preimplantation period was studied using tritiated N-acetylglucosamine. In vivo labelling was achieved by the intra-uterine implantation of agar gel columns containing the precursor. Autoradiography showed the radioactivity to be predominantly localized in the apical cell surfaces, with single cells exhibiting an accumulation of silver grains in their supranuclear cytoplasm. After gel electrophoresis of uterine flushings, activity was mainly found in the beta-glycoprotein fraction. Fluorescein isothiocyanate (FITC)-conjugated wheat-germ agglutinin reacted with the apical cytoplasm and surfaces of the endometrial cells. However, FITC-conjugated concanavalin A exhibited a different binding pattern, reacting first with the basal cytoplasm, and later with the apical cytoplasm. After concanavalin-A staining, single cells exhibited positive vesicles in their lateral and apical parts. These cells may be released into the uterine lumen until 210 h post column. Neither of the lectins reacted with ciliated cells. Concanavalin A showed an affinity for the beta-glycoprotein fraction of the uterine secretion. The results indicate that, although all endometrial cells contain glycoproteins, only a few of these seem to be involved in the synthesis of secretory products.