Colony-stimulating factor (CSF) in the uterus of the pregnant mouse

During the growth of the pregnant uterus of inbred Balb/c mice uterine colony-stimulating factor (CSF) content increased 800-fold. This corresponded to a 75-fold increase in CSF concentration. The size of the increase was the same in the uteri of inbred Balb/c mice and the uteri of F1 hybrid C57Bl/Balb/c mice mated with F1 males. It was about four times greater in these uteri than it was in the uteri of randomly mated TO mice. After unilateral Fallopian tubal ligation of TO mice the concentration of CSF was as great in the non-gravid uterine horns as it was in the gravid uterine horns. Physicochemical characterization of CSF from extracts of pregnant uterus showed that it differed from that found in foetal extracts and that found in the circulation. Its function in the pregnant uterus is discussed.