In utero haemopoietic sensitivity to alpha, beta or X-irradiation in CBA/H mice

Abstract

Purpose : To assess in utero sensitivity to x-rays, α -emissions from plutonium-239 and β -emissions from tritium in terms of induction of chromosomal aberrations in bone marrow cells. Materials and methods : CBA/H mice were exposed to a single dose of X-rays (0.5Gy) on either day 7 or day 14 of pregnancy or given 239 Pu (100 kBq kg -1) by intraperitoneal injection on either day 6 or day 13. Tritium was administered to mice throughout pregnancy as either tritiated water, ad libitum in drinking water (total intake averaged 130 MBq), or as homogenized tritiated cress, administered by gastric intubation (total 60 MBq). Irradiated and unexposed control mice and their offspring were sacrificed at 2-8 weeks after birth. Direct metaphase preparations from femoral bone marrow cells from mothers and offspring were used for G-band analysis. Results : The incidence of stable aberrations was significantly and similarly increased in neonatal and maternal marrow samples after exposure to X-rays, 239 Pu or 3 H. The estimated average bone absorbed doses from 239 Pu in pregnant females were similar to the X-ray dose of 0.5 Gy, suggesting a low RBE for α -irradiation in adults. The similar levels of damage observed in neonates after X-irradiation and 239Pu exposure are indicative of greater in utero sensitivity to α -irradiation since the overall estimated in utero α -particle doses to haemopoietic tissue were much lower. In utero doses from 3 H and corresponding maternal doses were around 0.5Gy, showing no evidence of greater in utero sensitivity, no significant difference between the effects of the two forms of tritium, and were consistent with an RBE value of 1-2. Conclusions : Comparison of stable aberration yields in haemopoietic cells suggests a greater sensitivity to α -particles from 239 Pu than X-rays or β -particles from 3 H for irradiation in utero but a low RBE value in adults.