Effect of retinoic acid on limb regeneration in Xenopus laevis
The objective of this experiment was to determine the effect of retinoic acid on the process of limb regeneration in the African clawed frog, Xenopus laevis. Limbs were bilaterally amputated through the radio-ulna and then treated for 15 days with retinoic acid in the aquarium water, at 3, 15, or 75 IU/mL. The retinoic acid inhibited limb regeneration in a dose-dependent manner, reduced the length of the regenerates, and produced irregularities in the morphogenesis of the cartilage rod in the regenerate. The regenerated limbs were removed after 150 days by amputation through the humerus, and the limbs were again allowed to regenerate. In the retinoic acid treated animals, despite the fact that retinoic acid treatment had been discontinued over 4 months previously, limb regeneration was still inhibited. These results suggest that retinoic acid has a long-term effect on the treated animals.