Changes in the cell population of the pregnant rodent uterus in relation to the differentiation of granulated metrial gland cells.

A time-lapse autoradiographic study has been made of changes in the cell population of the decidua basalis during its development in the mouse, in order to investigate the origin of granulated metrial gland cells. Granulated metrial gland cells initially formed less than 1% of the cells but during the period of study they increased in number to form 14% of the cells. The proportion of unlabelled lymphocyte-like cells and granulated metrial gland precursor cells fell significantly during the period of study. One hour after a single injection of tritiated thymidine on day 4 1/2 of pregnancy the proportion of labelled cells which were granulated cells was not significantly different from the proportion of total cells which were granulated cells. However, 84 hours after the injection of thymidine the proportion of labelled cells which were granulated cells was significantly lower than the proportion of total cells which were granulated cells. Similar results were obtained from studies of the developing metrial gland of the mouse and rat. The significance of the results in relationship to an extrauterine origin for granulated metrial gland cells is considered.