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

Purpose: To assess in utero sensitivity to x-rays, alpha -emissions from pl utonium-239 and beta -emissions from tritium in terms of induction of chrom osomal aberration sin bone marrow cells. Materials and methods: CBA/H mice were exposed to a single dose of X-rays ( 0.5 Gy) on either day 7 or day 14 of pregnancy or given Pu-239 (100 kBq kg( -1)) by intraperitoneal injection on either day 6 or day 13. Tritium was ad ministered to mice throughout pregnancy as either tritiated water, ad libit um in drinking ater (total intake averaged 130 MBq), or as homogenized trit iated 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 similarl y increased in neonatal and maternal marrow samples after exposure to X-ray s, 239Pu or H-3. The estimated average bone absorbed doses from 239Pu in pr egnant females were similar to the X-ray dose of 0.5 Gy, suggesting a low R BE for alpha -irradiation in adults. The similar levels of damage observed in neonates after X-irradiation and Pu-239 exposure are indicative of great er in utero sensitivity to alpha -irradiation since the overall estimated i n utero alpha -particle doses to haemopoietic tissue were much lower. In ut ero doses from H-3 and corresponding maternal doses were around 0.5 Gy, sho wing 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 haemopoetic cells su ggests a greater sensitivity to alpha -particles from Pu-239 than X-rays or beta -particles from H-3 for irradiation in utero but a low RBE value in a dults.