Cardiovascular defects in rat embryos cultured on serum from rats chronically exposed to phenytoin.

Headfold-stage rat embryos were cultured for 48 hours on serum from rats chronically exposed to phenytoin for periods as long as from conception until 11 months of age. Serum from phenytoin-exposed rats caused approximately 50% of the cultured rat embryos to develop cardiovascular defects as compared to 12% for controls. These morphological abnormalities included hemorrhaging of blood vessels within the embryo, pericardial edema, and absence of yolk sac circulation. Neither serum glucose nor phosphate levels nor serum osmolality were appreciably affected by phenytoin treatment. However, serum protein concentration was reduced in rats exposed to phenytoin as compared to controls. An absence of the serum protein hemopexin was associated with the reduction in serum protein levels but did not appear to be responsible for the observed cardiovascular defects.