CELL-DEATH IN RAT AND MOUSE EMBRYOS EXPOSED TO METHANOL IN WHOLE-EMBRYO CULTURE

Methanol induces developmental toxicity in rats and mice producing exe ncephaly, cleft palate, cervical skeletal defects, reduced body weight , and increased embryo/fetal death. Exposure to methanol in whole embr yo culture also induces developmental retardation, dysmorphagenesis, a nd embryo lethality. In the present study, cultured rat and mouse embr yos were exposed to methanol and subsequently observed for morphologic al effects and increased cell death using modified Feulgen staining wh ich allowed nuclei throughout the embryo to be examined in situ. Growt h and developmental scores were reduced by methanol in both rat and mo use embryos and the mouse embryos were affected at lower concentration s when compared to the rat. Methanol increased cell death in specific regions of both rat and mouse embryos, including the forebrain, the vi sceral arches, otic and optic placodes. These regions form derivatives which manifest morphological abnormalities following exposure in vivo . Methanol did not increase cell death in the neuroepithelium or neura l folds and neural tube defects cannot be explained by excess cell dea th. The results of this study suggest that increased cell death in spe cific regions of the exposed embryos has a role in producing cranial m alformations, abnormalities of the eye and ear, and cleft palate.