In order to elucidate the effect of chorioallantoic and yolk sac placenta on the embryonic/fetal toxicity in dibutyltin dichloride (DBTCl)-exposed rats, we examined the histopathological changes and the tissue distribution of dibutyltin in the placentas and embryos. DBTCl was orally administered to the groups at doses of 0 mg/kg during gestation days (GD)s 7-9 (control group) and 20 mg/kg during GDs 7-9 (GD7-9 treated group), and GDs 10-12 (GD10-12 treated group). The total fetal mortality was increased, and malformations characterized by craniofacial dysmorphism were detected in the GD7-9 treated group. The embryonic/fetal weight and placental weight showed a decrease in both DBTCl-treated groups. Histologically, some embryos on GD 9.5 in the GD7-9 treated group underwent apoptosis without any changes of yolk sac. In the laser ablation-inductively coupled plasma-mass spectrometry analysis (LA-ICP-MS), tin was detected in the embryo, allantois, yolk sac, ectoplacental cone and decidual mass surrounding the conceptus on GD 9.5 in the GD7-9 treated group. Thus, it is considered that the embryo in this period is specifically sensitive to DBTCl-induced apoptosis, compared with other parts. The chorioallantoic placentas in both DBTCl-treated groups showed the developmental delay and hypoplasia in the fetal parts of placenta, resulting from apoptosis and mitotic inhibition. Thus, it was speculated that the DBTCl-induced malformations and fetal resorption resulted from the apoptosis in the embryo caused by the direct effect of DBTCl. The DBTCl-induced lesions in the chorioallantoic placenta were a non-specific transient developmental retardation in the fetal parts of placenta, leading to intrauterine growth retardation.
Keywords: Dibutyltin; LA-ICP-MS; Malformation; Placenta; Rat.