Abstract: AIM: To observe the apoptotic cells of fetal spinal cord and define apoptosis of spinal cord by cyclophosphamide and make initial investigation in mechanism. METHODS: During the embryo-fetal development toxicity test, the CP experimental group was injected with CP 7.2 mg/kg and 9.0 mg/kg in the morning of day 10 of gestation;dissected pregnant rats on the day 20 of gestation for fetal spinal cord which were made HE staining and immunohistochemistry. RESULTS: A great quantity of apoptosis cells were observed in experimental group. Compared with negative control physiologic saline group, Bax expression in thoracic cord and isthmus cord anterior horn cell of low-dose CP group increased significantly (P<0.01), and Bcl-2 expression in thoracic cord and isthmus cord anterior horn cell of low-dose CP group are lower (P<0.05). CONCLUSION: These findings suggested that rats injected with CP 7.2 mg/kg in the morning of day 10 of gestation which can aggravate the apoptosis of fetuses' spinal nerves.

Key words: Safety evaluation, Cyclophosphamide(CP), Teratotoxicity test, Spina bifida, Apoptosis