[Placental transfer and mammary excretion of [14C] T-3761 in rats and mice].

Placental transfer and mammary excretion of radioactivity were investigated in the pregnant rats on day 19 of pregnancy, in the pregnant mice on day 18 of pregnancy, and in the lactating rats after oral administration of 5 mg/kg of [14C] T-3761. 1. Transfer of radioactivity to fetus was observed in rats and mice and the concentration in fetus was 0.2-0.5 times higher than the maternal plasma. 2. The radioactivity was excreted into the milk and the concentration in milk was higher than those of blood levels (milk/blood = 1.3-5.8). The radioactivity in milk declined more slowly than in blood.