Mutagenic effect of 131I in the mouse assessed by the transplacentar micronuclei test.

The incidence of chromosomal aberrations induced by 131I in the mouse foetus was assessed using the transplacentar micronuclei test (the incidence of the micronuclei in foetal liver). For comparison the standard micronuclei test was applied to the maternal bone marrow. A distinct quantitative difference was found with respect to the incidence of micronuclei in the foetus and the mother in response to doses of 131I as low as those used in clinical investigation. The less marked mutagenic effect of 131I on the foetus may be accounted for by the massive concentration of 131I in the mothers' thyroid and its increased renal clearance. A protective role might be also played by the placenta.