Distribution of 2,4,5-trichlorophenoxyacetic acid in the mouse fetus

The herbicide 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) readily crosses the placenta in the mouse on gestational day 13. Concentrations of 2,4,5-T in maternal tissues and fetuses were obvious at 30 min, highest at 8 h, diminished by 24 h and almost entirely eliminated by 48 h. Autoradiographs of the whole fetus showed that initially 2,4,5-T was mainly in the highly vascularized tissues such as liver followed by the skin, eyes and ventricles of the brain. At 48 h, there was a general distribution of 2,4,5-T in the skeletal muscles. None was detected in the palate. The excretion rate in the mouse was approx. 60 gm/h; about 52% of the dose was recovered unchanged in the urine in 24 h.