Comparative study of sodium valproate-induced skeletal malformations using single or double staining methods

The teratogenic activity of xenobiotics is usually investigated by examining visceral and skeletal abnormalities of term fetuses. Although the rodent fetal skeleton is only partially ossified, the single stain for bone is the most commonly used method in routine teratology testing, while the double stain for evaluation of both bone and cartilage is often used only in basic research. The present work compares data obtained from rat fetuses using the two methods after exposure to the teratogenic agent sodium valproate at specific embryonic stages of development. Pregnant rats were treated with 400mg/kg sodium valproate and sacrificed at term of pregnancy. Even if both methods were able to identify sodium valproate as a teratogenic molecule, correct and complete interpretation of data was possible only by using the double stain. Our results show the inability of the single stain to correctly discriminate between major and minor abnormalities.