Abstract
Administration of pregnant rats with cytosine arabinoside (ara-C) on day 11 produced preaxial polydactyly (87.9%) and on day 12 or 13 led to oligodactyly formation (day 12, 57.3%; day 13, 86.8%) in the hindlimb. However, the repeated treatments on 2 days 11 and 12 or 11 and 13 not only converted the polydactyly-inducing effect into the oligodactyly-inducing effect, but also reduced (49.2%, on days 11 and 12) or increased (100%, on days 11 and 13) the incidence of total digital malformations compared with that of single treatment on day 11, 12 or 13. This outcome might be due to the different susceptibility of the ectodermal and the mesodermal cells to the teratogen, because the stage of cellular differentiation was found to be different between the ectoderm and the mesoderm of the hindlimb bud. Although digital malformations produced by repeated treatments show more complex features than those produced by a single treatment, such experiments might be helpful to understand the pathogenesis of human digital malformations which are often too complex to be classified.
