ALL-TRANS-RETINOIC ACID-INDUCED VARIANT PATTERNS OF PALATAL RUGAE IN CRJ-SD RAT FETUSES AND THEIR POTENTIAL AS INDICATORS FOR TERATOGENICITY

We determined the critical period for cleft palate formation in the pr esence of all-trans-retinoic acid (RA) and defined anomalous patterns within the variants of palatal rugae. The total incidence of variant p atterns of palatal rugae in rat fetuses treated with RA at 40 mg/kg on gestation days 13 and 14 dramatically increased with concurrent induc tion of cleft palate, Correspondence analysis connected the variant pa tterns of palatal rugae, such as median discontinuity, extra peaks, su pernumerary ruga (extra type), shortness, fusion, and bifurcation, wit h cleft palate. Therefore, these variants were concluded to be anomalo us. The incidence of the anomalous patterns of palatal rugae was about 10 times that of cleft palate, and consequently, these anomalies migh t be sensitive indicators of the teratogenicity of a chemical.