Involvement of lysosomal enzymes in mouse embryo implantation: effect of the anti-oestrogen, CI-628 citrate.
Implantation of embryos was studied in mice which had bee ovariectomized on the afternoon of day 4 of pregnancy and injected intraperitoneally with a non-steroidal antioestrogen or control injection. Normal implantations were obtained in the latter mice as indicated from the positive blue-dye sites when animals were killed late in the evening of day 4. Exposure to CI-628, however, led to a significant inhibition in the number of implantations and only a small percentage of the mice exposed to the steroid antagonist showed normal implantation sites. Study of a few lysosomal enzymes in uterine tissues at the time of early embryo attachment revealed a striking change in the activity of leucyl naphthylamidase. The enzyme showed a reduction in its activity only in uterine which contained attached blastocysts. Acid phosphatase, beta-glucuronidase and non-specific esterase did not show any such implantation-specific changes in their activity patterns. A possible role of leucyl naphthylamidase in the attachment of the embryo to the wall of the uterus has been explored.