Unmasking of surface negativity on day 6 pregnant rat uterine epithelial cells by trypsin and pronase.

Cationic Ferritin and Ruthenium Red were used to label rat uterine luminal epithelial cells at estrus and 6th d of pregnancy. Labelling was heavy at estrus and light on 6th d. Trypsin and pronase reduced labelling at estrus and restored labelling at 6th d suggesting that negatively charged carbohydrates may become masked at the time of implantation.