Abstract
Methylmercuric chloride (MMC) induced cleft palate in all ICR mouse fetuses, when given orally as a single dose of 25 mg/kg to the mother at an appropriate day of pregnancy. The critical period of MMC administration to the ICR dams to induce 100% cleft palate in their offspring was from day 10 to 12 of pregnancy (plug day=day 0).
Normal palate closure in the ICR fetus occurred on day 14 of gestation. However, fetuses from dams treated with MMC on day 10 of pregnancy failed in palate closure because the palate shelf horizontalization was delayed so seriously that the bilateral palate shelves could not fuse with each other. This suggests that MMC may act to retard the movement of the palate shelf from the vertical to horizontal plane in ICR mice.
