Distribution of carbon-14 and associated radiation dose in rat fetal brain and liver after maternal injection of [14C]thymidine.

Pregnant Sprague-Dawley rats were injected intravenously with [14 C]thymidine on day 13.5 of gestation, and the concentrations and radiation doses of14 C in the fetal brain and liver were determined by liquid scintillation counting and autoradiography with imaging plates. The concentrations of14 C in the whole fetal brains determined by liquid scintillation counting were 1.01% of the injected dose per gram wet weight at 6 h after injection and decreased to $0.39\%\ {\rm g}^{-1}$ at 48 h after injection. A significant accumulation of14 C was observed in the fetal liver: 3.8 and 0.51% of the injected dose per gram wet weight at 6 and 48 h after injection, respectively. Autoradiography showed that, especially at earlier periods after injection, there was remarkable concentration of14 C in the ventricular zone of the brain and the central region of the liver. With increasing time after injection, the distribution of14 C became relatively uniform. The concentrations of14 C in the ventricular zone of the fetal ...