Effect of an oestrogen antagonist on implantation and uterine leucylnaphthylamidase activity in the ovariectomized hamster.

CI-628 citrate, an oestrogen antagonist, instilled into the uterine lumen of ovariectomized, progesterone-treated hamsters on Day 3 of pregnancy completely prevented implantations. Normal implantations occurred in the contralateral uterine horn which was pierced by a needle and in horns into which saline was instilled. There was less activity of lysosomal leucylnaphthylamidase in implantation sites than in inter-implantation sites and in the tissues of the CI-628 citrate-treated horns.