Changes of progesterone receptors in mesometrial and antimesometrial deciduoma after removal of fetus or placenta in unilateral pregnant hamster.

The effects of fetuses or placentas (with fetuses) removal on progesterone receptors (PR) in deciduomal tissues were investigated in unilateral pregnant (ULP) hamsters. Deciduomal reactions in response to artificial stimuli were induced on the tube-ligated uterine horns of ULP hamsters. Fetuses or placentas (with fetuses) were removed on day 8 of ULP, and the cytosolic and nuclear PR (cPR, and nPR, respectively) levels in deciduomal tissues at mesometrial (MS) and antimesometrial (AMS) sites were separately studied on day 10 and 12 of ULP. In the sham control group, cPR at the MS decreased with time, but at a slower rate than that at the AMS. The MS deciduoma contained higher cPR than the AMS deciduoma on day 12. Removal of fetuses did not cause any significant change of the decline rate, and the PR levels were similar to that of the control. The nPR at the MS and AMS also declined with time in all three groups. Removal of placentas induced drastic losses of cPR and nPR at the MS and AMS on day 10 and 12. Supplement of progesterone (P; 2 mg/animal/day) to the placenta-removed group restored the cPR somewhat at the MS site, but not back to the level of the control. The effect of P to restore nPR levels could be observed at the MS and AMS on day 10, but only at the MS on day 12. These data suggest that placental factor(s) other than P may play an important role on the maintenance of PR in deciduoma. Other cellular mechanisms may exist at the MS and AMS sites for the heterogeneous responses.