Comparative placental transfer, localization, and effects of radionuclides in experimental animal and human pregnancies

摘要

Estimating radiation doses to the human embryo/fetus from radionuclides and predicting effects requires extrapolation of data from studies of laboratory species, with scaling for species-specific developmental stage and gestational time relationships and maturities at birth. Combinations of fetal-to-maternal ratios of concentrations, patterns of deposition, transfer kinetics, and compartmental and physiologic models are used to predict radioactivity levels and radiation doses to the conceptus. There is agreement between values expressing fractional transfer across the placenta ((theta)) with tabulated values for fractional absorption (f(sub 1)) from gastrointestinal (GI) tract or lung for most substances commonly involved in metabolic processes. A tendency toward disagreement for some other materials is thought to involve explanations based on their physicochemistry, toxicity, or the influence of target tissue development on placental transfer kinetics.