Changes in RNA polymerase activity in isolated mouse uterine nuclei during the decidual cell reaction

The artificially stimulated decidual cell reaction has been used as a model to study changes occurring in the uterus at the time of implantation. Activities of RNA polymerases I, II and III were measured in uterine nuclei isolated from ovariectomized non-primed mice, hormonally primed mice, and hormonally primed mice following stimulation of the decidual cell reaction. Activities of all three RNA polymerases increased following hormonal priming of ovariectomized mice. In nuclei from stimulated uterine horns, activities of RNA polymerases I and III increased 9 h after stimulation of the decidual cell reaction and remained elevated through 21 h. RNA polymerase II activity did not change following stimulation of the decidual cell reaction. These changes in RNA polymerase activities occur at the time of increased histone modifications and may result from changes in the template capacity.