Abstract
Because of rapid increase in the frequency of medical exposure to radiation, the effects of radiation on children have become a great concern in recent years. However, there is little information about this. We therefore started to study the radiation effects on children. The aim of this study is to demonstrate an age dependency of hepatocyte response to radiation in B6C3F1 mice. First, we investigated normal development of liver from fetal to adult stage histologically. There were many hematopoietic cells together with highly proliferating immature hepatocytes in fetal liver. Immature bile ducts and hepatic cords were formed within 1 week after birth. At 7 weeks of age, morphologically matured hepatic lobes were formed. Next, we investigated the hepatocyte response to radiation in terms of proliferation and apoptosis by immunohistochemical analysis using antibody for p53, Ki67, active caspase3, PCNA, and gamma-H2AX. We found that hepatocytes in 1-week-old mice were resistant to radiation-induced cell cycle arrest, which may account for, at least in part, high susceptibility of immature hepatocytes to radiation-induced hepatocarcinogenesis.
