Intravitelline injection of rodent conceptuses: An improved in vitro developmental toxicity screen

Many in vitro developmental toxicity screens are of limited usefulness, either because they lack the cell interactions of a whole embryo or because it is difficult to attribute an effect to the substance itself or a generated metabolite. Intravitelline injection into rat conceptuses during organogenesis bypasses the metabolically active visceral yolk sac and allows accurate delivery of specific drugs or their metabolites directly to the embryo. In a blind trial using 31 coded compounds, an overall accuracy of approximately 74% was achieved and four pairs of active/inactive analogues were distinguished. Additionally, thalidomide was shown to have teratogenic effects at low doses, mainly in the neural tube region.