In vitro approaches in developmental toxicology.

While the usefulness of in vitro screens in developmental toxicology seemed obvious a decade or more ago, integration of in vitro or short-term screens for developmental toxicity into the toxicology armamentarium of tests has been very slow. The large number and complexity of critical events in normal development in vivo limit the usefulness of in vitro systems that measure a very narrow range of developmental events, even though such systems are very useful for mechanistic research. Better understanding of the regulatory mechanisms involved in normal development that is evolving from molecular and developmental biology laboratories should help to identify critical events and processes in development that could serve as functional screens for abnormal development in the future.