ABSTRACT
The utility of in vitro developmental toxicity assays can be tested only by comparing their outcomes with those of standardized in vivo developmental toxicity studies. To appreciate the advantages and limitations of in vitro developmental toxicity methods as screening tests, it is necessary to review the practical use and limitations of standard in vivo safety evaluations. For individualized counseling, it perhaps is not surprising that the highly manipulable in vitro methods can have greater utility than tests made in intact pregnant animals. The most consistent method for both developmental and adult no observed-adverse-effect-level determination is the mode used by national and international regulatory agency personnel in face-to-face encounters with manufacturers of specific chemicals. Another screening type assay that merits mention in the context employs blastula stages of the Xenopus frog and is called the Frog Embryo Teratogenesis Assay. Assays that purport separation of teratogens from non-teratogens are incompatible with experience that began at the very onset of experimental developmental toxicology.
