Abstract: The micromass culture was used to determine the effects of vanadium pentoxide(v2O5)on the proliferation and differentiation of limb bud cells of rat．In the in vitro test,the results showed that V2O had obvious inhibiting effects on both proliferation and difierentiation of limb bud cells with a dose-dependent response，its proliferating and differentiating IC50 being 13．64 and 4．77 Vmol／L，respectively． In the in vivo/in vitro test，the results showed that V2O5 had no obvious effect on cell proliferation but had obvious inhibiting effect on cell differentiation．These results indicated that V205 might have a specific inhihifing effec t on the differentiation oflim b bud cells．

Key words: micromass culture, limb bud cells, developm ental toxicity, V2O5, rat