Luteolytic influence of intrauterine dead embryos in the early pregnant rat.

The present investigation was an endeavour to study if annihilation of embryos in the uterus of the rat before the establishment of placental luteotropic functions has any influence on corpus luteal function, and, if there is any, whether it is local or systemic. The responsibility of pregnancy maintenance was imposed on a single ovary by performing unilateral ovariectomy after implantation (on Day 5 postcoitum). The implantation sites in one uterine horn, either ipsilateral or contralateral to the remaining ovary, were selectively destroyed by injecting 0.1 ml of sterile normal saline to that particular horn only, and the peripheral progesterone level and viability of the embryos in the untreated horn, which depended on the functions of the remaining ovary, were examined. Selective killing of embryos in the uterine horn of the ovariectomized side did not exert any influence on the fetal viability in the untreated horn ( nonovariectomized side) and the peripheral progesterone level also remained statistically unaffected. On the contrary, induction of fetal resorptions in the uterine horn of the intact side produced a significant fall in the peripheral level of progesterone and induced resorption of embryos of the ovariectomized side also. The latter could significantly be prevented by simultaneous administration of exogenous progesterone, indicating luteolysis as the major, if not sole, factor responsible for fetal resorption in the untreated horn. The luteolytic effect was attributed neither to saline itself, nor to the distension of the uterine horn caused by saline injection. Luteolytic factors from the dead embryo-bearing horn which act locally on the adjacent ovary only, are discussed.