Induction of cleft palate by gamma-irradiation of prenatal CD-1 mice.

Fetuses of pregnant mice exposed to whole body gamma-irradiation (400 rads) on the 12th gestational day were compared with control fetuses to assess the effect of radiation on palatogenesis. Experimental and control groups were sacrificed on day 18 of gestation. The fetuses were removed via laparotomy and counted to determine the litter size. Animals were decapitated and the maximum head height, width, and circumference recorded. For light microscopic examination of palatogenesis, heads were fixed in Bouin's solution and prepared for paraffin sectioning and staining with hematoxylin and eosin. A significant reduction in litter size (p < .0025) and head measurements (p < .005) of irradiated fetuses was observed when compared to those of the control group. Histologic examination of serial coronal sections demonstrated that 100% of the experimental fetuses had palatal clefts. It was concluded that gamma-rays have adverse effects on the litter size, head measurements, and palatal closure of mouse fetuses.