REACTION OF THE MOUSE UTERUS DURING IMPLANTATION AND DECIDUOMA FORMATION AS DEMONSTRATED BY CHANGES IN THE DISTRIBUTION OF ALKALINE PHOSPHATASE

Using a histochemical technique, alkaline phosphatase has been shown to appear in the stroma of the mouse uterus during implantation and after initiation of the oil-induced deciduoma. In sections of pregnant uteri the enzyme first appeared on the 5th day after mating as a small crescentic area in the stroma on the antimesometrial side of the uterus close to the implanting blastocyst. In pseudopregnant mice after instillation of oil into the uterine lumen (on the 4th day) a similar crescentic area of alkaline phosphatase activity appeared around the uterine lumen on the antimesometrial side on the 5th day. The epithelium in both cases is intact on the 5th day but degeneration occurs on the antimesometrial side on the 6th day. This suggests that epithelial degeneration is an inherent property of the uterus during the period of implantation, and is not directly caused by the activities of the giant cells of the trophoblast. There was no alkaline phosphatase activity in the uterine stroma of pseudopregnant untreated mice on the 4th, 5ht and 6th days after sterile mating and the epithelium showed no evidence of degeneration. Further, injection of oil into the uteri of ovariectomized mice failed to