Maternal transfer of¹⁴C-p,p′- DDTvia Placenta and milk and its metabolism in infant rats

Abstract

Female rats were dosed orally with 0.9 mg¹⁴C-ring-labeledp,p′-DDT during pregnancy or lactation. The results from the lactation experiment showed that the mean concentration of¹⁴C-DDT in milk was 15.26Μg per g dry weight the first day after dosing, and decreased gradually with a rate constant of clearance of −0.096. The half-life of DDT and its metabolites in milk was approximately 7.2 days. Neonatal rats, sacrificed after 1 to 28 days, showed that the maximal concentration of¹⁴C was generally reached in 1 to 3 days then declined at a rate comparable to that in milk. Liver, intestine, and carcass had the highest radioactivity; next, in decreasing order, were lung, kidney, heart, brain, and blood. In the liver of the neonate, the relative concentration of DDT was decreased from 100% in the first day to 44% in the 28th day, while DDD and DDE increased gradually to 36% and 22%, respectively. In the experiment with pregnant rats, the results showed that DDT was readily absorbed, transported throughout the whole body, and deposited in the fetuses. The average biological halflife of DDT in various tissues and the fetus was 10.6 hr. DDT was converted more rapidly to DDD, DDE, and two minor unidentified metabolites in the adult liver than in the liver of neonates. DDE and DDD were also found in other tissues and fetuses of pregnant rats. The relative amounts of DDE and DDD varied in different tissues. DDA was not present in all tissues examined. In the placenta and fetuses, it was only detectable, whereas in the lung, intestine, blood, and kidney, it was a major metabolite.