Development of the mouse blastocyst after actinomycin D treatment

Mouse blastocysts were incubated in vitro with actinomycin D in concentrations of 10-1 to 10-5 mug/ml. After transfer to recipient animals, there was a moderate but significant decrease in implantations at 10-minus 1 to 10-minus 3 and 10-minus 5. There was a severe inhibition of subsequent development at concentrations of 10-minus 1 and 10-minus 2. One of 49 fetuses which developed after actinomycin D treatment had a major malformation; there was one major and one minor abnormality among 95 control fetuses. It is suggested that most of the RNA or protein required to effect implantation is synthesized or coded for prior to the blastocyst state. The moderate but significant decrease in implantations found after actinomycin D treatment at this stage may reflect the ability of the drug to reduce cell adhesiveness. This study confirms the impression that the preimplantation embryo is relatively impervious to teratogenic agents, even one as potent as actinomycin D.