IMPLANTATION AND ATTACHMENT REACTION OF RAT UTERINE LUMINAL EPITHELIUM AT A HIGH

The injection of 5 \g=m\goestradiol to progesterone-treated spayed, pregnant rats caused implantation in some rats but not in others. In rats with im-plantation the epithelium underwent a change similar to that during normal implantation, i.e. an attachment reaction. No attachment reaction was seen in rats without implantation or in progesterone-treated, spayed, virgin rats. The results may support the idea that the attachment reaction is the morphological sign of a receptive uterus and that the reaction is functionally related to the onset of implantation. Further, they indicate that the sensitivity to oestrogen varies between rats during delayed implantation