HEMATOLOGICAL RECOVERY OF MOUSE FOLLOWING FETAL X-RADIATION

¹ Radiological Research Laboratory, Department of Radiology, College of Physicians and Surgeons, Columbia University, 630 West 168th St. New York, N. Y. 10032

1. In the fetus at 17 days, two days following x-irradiation in utero (at 15 days), there were increments in the white cell counts correlated with the level of exposure to x-rays, after both 50 R and 100 R. This is in contrast to the expected reaction of adult mice of the same strain.

2. At 17 days the erythrocyte counts showed a significant depression following 100 R exposure at 15 days' gestation. This too is in contrast with the adult reaction.

3. All platelet counts of those mice x-rayed at 15 days and examined at 17 days' gestation were depressed below the control levels, but by 3 weeks post-natal development they were within the normal range.

4. Both red and white blood cell counts of fetally x-rayed mice returned to normal by 3 weeks after birth.

5. Exposure of the 15-day fetus resulted in a defensive reaction expressed in temporary leukocytosis, as opposed to the normal leukopenia of adult mice similarly exposed, but by 3 weeks of post-natal age both the differential and all other cell counts were within the normal range. This means that effects on the fetal blood (hematopoiesis) are temporary, since there was no evidence of any mortality at the levels of radiation used nor of any permanent effects on the blood counts.