Stage specificity of Ara-C induced carpal and tarsal bone anomalies in mice

Pregnant mice were injected intraperitoneally with a single dose of 5 mg/kg of cytosine arabinoside (Ara-C) on different gestational days (dg 9-12). On the 15th postnatal day, skeletal anomalies of the paws were examined, and associations between carpal and tarsal bone anomalies and digit anomalies were assessed. The types of carpal and tarsal bone anomalies differed according to the time of exposure to Ara-C during pregnancy. It was also found that the "critical period" for the carpal and tarsal bones is wider than that of the digits. The occurrence of anomalies of phalangeal and metacarpal/metatarsal bones was always associated with carpal or tarsal bone anomalies, although some carpal and tarsal bone anomalies occurred alone. It may be that the Ara-C threshold is considerably lower in the carpal and tarsal bones than in the digits.