X-ray induced mutation in Syrian hamster fetal cells.
Transabdominal X-rays are a risk factor for childhood leukemia, and X-ray exposure of mouse fetuses has led to increases in both mutations and initiated tumors in offspring. However, fetal sensitivity and dose-response characteristics with regard to transplacental mutagenesis by X-rays have never been quantified. In the current experiment, pregnant Syrian hamsters at day 12 of gestation were irradiated with 300-kV X-rays. Twenty-four hours later, the fetuses were removed and their cells were allowed a 5 day expression time in culture. They were then seeded for colony formation and also for mutation selection by 6-thioguanine (6-TG). Mutation frequency was linear over the entire dose range, 10-600 R. The average induced 6-TG mutant frequency was 4.7 x 10(-7) per R. These results suggest that fetal cells are highly sensitive to induction of mutations by X-rays, and that a no-effect threshold is not likely. The 10 R dose caused a 25-fold increase in mutation frequency over the historical control, 45 x 10(-7) versus 1.8 x 10(-7), an increase per R of 2.5-fold. Increased risk of childhood cancer related to obstetrical transabdominal X-ray has also been estimated at 2.5-fold per R. Thus, our results are consistent with mutation contributing to this effect.
Donovan
Paul J
PJ
Laboratory of Comparative Carcinogenesis, Department of Health and Human Services, National Cancer Institute at Frederick, Building 538, Room 205E, Frederick, MD 21702-1201, USA. donovapa@mail.ncifcrf.gov
Smith
George T
GT
D000818:Animals; D002460:Cell Line; D002470:Cell Survival / Q000528:radiation effects; D006224:Cricetinae; D004307:Dose-Response Relationship, Radiation; D005260:Female; D005333:Fetus / Q000528:radiation effects*; D005865:Gestational Age; D006801:Humans; D008647:Mesocricetus; D011247:Pregnancy; D014965:X-Rays