Response of early chick embryos to busulfan.

Busulfan, suspended in peanut oil, was injected into the yolk sac of white Leghorn chick embryos in dosages of 0.1 mg, 0.5 mg, or 1.0 mg. Embryos received a single injection of busulfan either prior to incubation, at 24, 48, 72, or 96 hours of incubation. Surviving embryos were sacrificed when they reached five days of incubation. Some embryos exposed to busulfan at 96 hours were allowed to develop to nine days of incubation to determine whether the time of initial exposure or the length of exposure to busulfan was more critical. The embryo required 48 hours to manifest the deleterious effects of busulfan. Abnormalities such as defects in the formation of the limb buds and cephalic hematomas were commonly seen in survivors no matter when exposed to busulfan. Some embryos injected at 96 hours and allowed to develop to nine days displayed edema of the body cavities. The role of busulfan in eliciting these malformations is discussed.