Effects of anticonvulsant drugs on fetal mouse palates cultured in vitro

Maxillary regions of day-12.5 ICR mouse fetuses were dissected and cultured in a chemically defined serumless medium, and the effects of anticonvulsant drugs on in vitro palatogenesis were studied. The explants were treated for 72 h in vitro with 50 to 200 micrograms/mL diphenylhydantoin (DPH), 200 to 800 micrograms/mL sodium phenobarbital (PB), 12.5 to 400 micrograms/mL sodium valproate (VPA), and 3 to 100 micrograms/mL diazepam (DAZ). During the culture, the secondary palatal shelves of control explants elevated, grew medially, and fused after 72-h culture in a manner similar to the palatogenetic process in vivo. The fusion of palatal shelves was inhibited dose-dependently by treatments with DPH, VPA, and DAZ. PB showed no significant inhibitory effects on palatal fusion at concentrations up to 800 micrograms/mL. The in vitro toxicity of the anticonvulsants tested appeared to correlate with the relative in vivo teratogenic potential of the drugs. The present study demonstrated that the in vitro organ culture system should be useful for screening teratogenic agents, especially those causing cleft palate, and for exploring the mechanisms of cleft palate formation.