Dose‐ and stage‐related sex difference in the incidence of cytosine arabinoside induced digit anomalies in the mouse fetus

Pregnant mice of the Jc1:ICR strain were injected intraperitoneally with a single dose of 2.5, 5, or 10 mg/kg of cytosine arabinoside (Ara-C) on day 9.5 or 10.5 of gestation (dg). Mice were killed on 18.4 dg, and the incidences of digit anomalies were compared between male and female fetuses. In the group treated with 10 mg of Ara-C on 9.5 dg, oligodactyly of the hindlimbs was produced more frequently in male fetuses. In the group treated with 5 mg of Ara-C on 10.5 dg, oligodactyly of the forelimbs tended to occur more frequently in male fetuses. Also, in this group, oligodactyly of the hindlimbs occurred more frequently in male fetuses, whereas polydactyly occurred more frequently in female fetuses. The observed difference in the incidences of digit anomalies between male and female fetuses may be explained either in terms of the sex-related time lag in the critical period for digit development or by a probable sex difference in embryonic susceptibility to Ara-C.