The teratogenic effects of 6‐mercaptopurine on chick embryos in ovo

Fertilized eggs of single-combed White Leghorn hens were each injected through a shell window directly beneath the embryo at 70 or 96 h of incubation with 2 mg of the sodium salt of 6-MP dissolved in 0.1 M phosphate buffer, and at 11 days of incubation the embryos were examined for gross morphological abnormalities. Various gross malformations and growth retardation were found, the most frequently and severely affected structures being limbs, beak, and eyes. Treatment at 70 h caused more severe abnormalities than at 96 h, but the spectrum of defects was not very different.