Production of Deciduomata in Ovariectomized Mice Receiving Progesterone. ∗

It has been recognized since the original experiments of Loeb 1 that the corpus luteum hormone is essential for the development of the maternal portion of the placenta. The belief has been quite general, 2 however, that this hormone must be supplemented by estrogen for the reaction to occur. Apparently the only instance of the induction of placentomata with progesterone alone is reported by Selye, 3 who traumatized the uterus of an ovariectomized rat receiving 15 mg of progesterone daily. In the experiments reported here much smaller amounts of progesterone were effective in eliciting the decidual reaction in uteri of mice traumatized longer than 2 months after ovariectomy.

The observations were made on 17 young adult, ovariectomized mice. Ten days after ovariectomy one horn of the uterus in 7 animals was slit throughout its length and 0.5 mg of progesterone† daily was injected subcutaneously beginning at operation. The 2 animals autopsied one day and one animal autopsied 2 days after operation showed developing deciduomata. One animal on the third day showed no decidual reaction. The remaining 3 animals had well developed deciduomata on the second, third, and fourth days.

In another group of 6 mice 68 days after ovariectomy one horn of the uterus was slit throughout its length and 3 sutures were placed in the other horn, and the animals were killed 6 days later. Daily injections of 0.5 mg of progesterone were started 7 days before operation in 4 animals and at operation in 2 animals and continued until autopsy. Six days after operation placentomata were found in 3 of the pretreated animals and in one of the 2 animals started on progesterone at operation.

In a final group of 4 mice 70 days after ovariectomy one horn of the uterus was slit and threads placed in the other horn as before. Progesterone was injected daily beginning 3 days before operation, the dose being 0.25 mg in 2 animals and 1.0 mg in 2 animals. At autopsy 3 days after operation deciduomata were present in 3 animals and absent in one of the animals receiving the lower dose.