Distribution and binding of 1, 3, 5 [U14C]-trioxane in maternal and fetal rats.

The tissue distribution and binding of 14C activity were studied at different time intervals following a single oral administration of 1,3,5[U14C]-trioxane (14C-TOX) (40 mg/kg: 1.6 MBq/kg) to pregnant rats. Animals were killed on the 21st day of gestation 3, 24, or 48 hours after administration of TOX. In maternal rats, 3 hours after administration, the highest levels of total radioactivity were found in the liver and plasma, followed by a slow, gradual decline with time. The level of 14C-activity in the whole fetus was comparable to that of the maternal kidney through the study. The radioactivity in the fetal kidney and liver at the end of 48 hours after single administration was higher than at 3 hours after administration. Slow decline in radioactivity was observed with time in the fetal brain, skin and carcass. However, after 48 hours the level of total radioactivity in the fetal kidney and brain was more than twice as high as in the corresponding maternal organs. Three hours following 14C-TOX administration 35-41% of the respective total 14C radioactivity in maternal liver and kidney was firmly bound to the macromolecules, while the fetal liver and kidney showed 100-72% binding with respect to their total radioactivity.