Objective: To define the optimal 2, 3, 7, 8-tetrachlorodibenzo-p-dioxin (TCDD) dose based on the morphological and histological changes of fetal mice cleft palate induced by different TCDD doses.
Methods: The pregnant mice were randomly divided into five groups and 6 in each grouop, and were gavaged on gestation day 10 (GD10). The control group were given 0.1 ml corn oil, and the experimental groups I, II , III, IV were given 32, 28, 24, 20 microg/kg TCDD respectively. To weight pregnant mice and embryos, record the number of live, cleft palate, dead and resorption fetal mice on GD 17.5. Another 15 pregnant mice were randomly divided into five groups (same as above) and 3 in each group. The coronal sections of the fetal mice heads were prepared at GD 13.5, 14.5 and 15.5 respectively, stained with haematoxylin-eosin staining (HE) and observed by microscopy.
Results: No significant differences in embryonic weight and live fetuses weight in each group. Compared with the control group,experimental groups I - III had small palate shelves (PS) and delayed palae shelves lift; the palate development and elevation in experimental group IV was similar to the control group. The incidence of cleft palate in the experimental groups I - IV were 97.37%, 93.02%, 65.12%, 56.82%, and no cleft palate in the control group.
Conclusion: The optimal dose of TCDD to induce cleft palate in C57BL/6J mice is 28 microg/kg.