Hyperploid cells in the limb buds of rats and 5-azacytidine-induced digital deformities

To clarify the mechanism underlying the digital teratogenesis of 5‐azacytidine (5‐AC), the DNA contents of mesenchymal cells were examined in the limb buds of the rat by microspectrophotometry. 5‐AC induced hyperploid cells: 2.4% at 18 h after injection and 3.2% at 24 h. No hyperploid cells were noted 30 h after the treatment. Because posttreatment caffeine suppressed 5‐AC‐induced digital defects, the actions of caffeine on 5‐AC‐induced hyperploid cells were further studied; no hyperploid cells were detected at any sampling point. Caffeine suppressed hyperploid cells as well as digital defects. These results suggest that the causative factors of digital defects by 5‐AC may involve hyperploid cells. However, in that there were too few hyperploid cells to cause the defects, further studies are required to clarify the nature of the action of 5‐AC. © 1992 Wiley‐Liss, Inc.