Epithelial cell death and cyclic AMP increase during palatal development.

Cyclic AMP levels increase abruptly in the secondary palatal shelf (mesenchyme plus a two- to three-cell-layered epithelium) between day 15 and 16 of gestation in the rat embryo. The addition of dibutyryl cyclic AMP to the media in which immature palatal shelves (day 14) are cultured causes a precocious decrease in DNA synthesis, but increased glycoprotein synthesis and epithelial adhesiveness. These changes are most evident in the medial-edge epithelial cells and resemble the developmental events that occur normally on day 15 and 16 during formation of the secondary palate. The initiation of epithelial cell death and adhesiveness in the medial edge of the palatal shelf may be mediated through an increase in cyclic AMP.