Objective   To investigate the effects of 4-nonylphenol(4-NP)on cultured rat embryos < I > in vitro < /I > and to explore its embryonic toxic mechanisms.

  Methods   the 9.5-day-old Wistar rat embryos were explanted and cultured at six different concentrations of 4-NP in rat immediately centrifugal serum(0, 6.25, 12.5, 25, 50, 100 mg/L)for 48 hours.Light microscope and electronic miroscope were used to observe structure of cultured embyos and their visceral yolk sacs (VYS).

  Results   4-NP athigher level(≥25 mg/L)could inhibit the growth and cardiac tube differentiation of VYS and increase abnormal embryos.Mutli-system abnormalities included neural tube defect, small heart, deficiency in axial rotation and small fore limb bud, etc.Under light microscope, 4-NP could result in apparent pathologic changes on VYS and brain, heart and arch of embryos, it was also observed that 4-NP could damage ultrastructure of VYS under scanning electronic microscope.There was a dose-response relationship between concentration of 4-NP and its embryonic developmental toxicity.

  Conclusion   4-NP could cause embryonic toxicity to cultured rat embryo athigher level.The damage of structure and function of VYS and the direct cytotoxicity induced by 4-NP may play a vital role in embryonic toxic mechanisms of 4-NP in vitro.