Relation between embryotoxicity of adenine in mice and day of prenatal treatment

Adenine (250 mg/kg) was given ip to ICR‐JCL mice on day 8, 9, 10, 11, or 12 of gestation. Near‐term fetuses were examined for external and skeletal malformations and the following noted. (1) A lethal effect occurred in all treatment groups except day 8 with the effect severest in day‐10 group. (2) The mean fetal weight was significantly decreased in all treatment groups, with this effect especially high in the day‐10 and −12 groups. (3) Day‐10 or −12 treatment caused high frequencies of external malformations. (4) Cleared specimens revealed that day‐8, −9, or −10 treatment induced a large number of vertebral malformations and there was a tendency of head‐to‐tail shift of malformations as time of administration advanced.