Effect of prenatal gamma irradiation during the late fetal period on the postnatal development of the mouse

Pregnant Swiss albino mice were exposed to 0.3, 0.5, 1.0, or 1.5 Gy of gamm a radiation on day 17 of gestation. Sham-exposed controls were examined for comparison; Exposed mice as well as controls were left to complete gestati on and parturition. Pups were observed up to age 6 weeks; appearance of phy siological markers (pinna detachment, eye opening, fur development, vaginal opening, and testes descent), postnatal mortality, body weight, body lengt h, head length, head width, and tail length were recorded. A significant de lay in fur development was observed at 0.3 Gy and in other physiological ma rkers at doses above 0.3 Gy, while a significant increase in mortality and growth retardation occurred only at 1.0 and 1.5 Gy. Although congenital ano malies such as syndactyly and bent tail were observed at doses of 0.5-1.5 G y, only syndactyly showed a statistically significant increase in frequency . A statistically significant lower body weight was observed during the fir st week of postnatal life, but body weights increased to normal levels by t he second week in animals exposed to doses less than 1.0 Gy. At higher dose s, low body weight persisted throughout the postnatal period. Head length a nd tail length showed a significant decrease from controls at 0.5-1.5 Gy, a nd the effect was evident from birth to age 6 weeks. But a similar effect o n body length and head width was noticed only at 1.0 and 1.5 Gy. These stud ies indicate that even in the absence of any major morphological changes, n ormal development of physiological landmarks and postnatal growth can be im paired by fetal irradiation at 17 days p.c. (post coitus). Morphological ch anges appear to have a threshold between 0.3-0.5 Gy, while physiological ma rker effects may occur with a lower threshold. (C) 1999 Wiley-Liss, Inc.