O或减少或增多［13］，机制尚不清。本实验结果提示DEX诱导巨噬细胞凋亡与NO生成增多有关。NO是一种自由基气体，其不成对电子在氮原子上，为氮自由基参与细胞内和线粒体内的链式反应，VitC为自由基链反应阻断剂，减轻损伤，能部分抑制巨噬细胞凋亡，细胞吞噬机能也获得部分恢复，以DEX组较显著。本实验提示VitC以抗氧化与抑制DEX诱导的M凋亡有关。推测环磷酰胺诱导腹腔巨噬细胞凋亡是以直接损伤染色体而DEX以氧化损伤为主，VitC以抗氧化作用而减轻DEX诱导的M凋亡。  【参考文献】    1  Pardue  SL， Thaxton JP. Evidence for amelioration of steroid-mediated immunosuppression by ascorbic acid. Poult Sci，1984，63(6):1262-1268.    2  Olson GE， Poik HC Jr.In vitro effect of ascorbic acid on corticosteroid-caused neutrophil dysfunction.J Surg Res，1997 Feb，22(2):109-112.    3  De Ia Fuente M，Ferrandez MD.Immune function in aged women is improved by ingestion of vitamins C and E.Can J Physiol Pharmacol，1998 Apr，76(4):373-380.    4  ERIC H.KRAUT. Antioidants and immune response in aged person:overview of present evidence.Am J Clin Nutr，1995 Dec，62(6 Suppl):1462-1476.    5  Rojas M ，Rugeles MT.Differential modulation of apoptosis and necrosis by antioxidants in immunosuppressed human lymphocytes.Toxicol Appl Pharmacol 2002 Apr 15:180(2):67-73.    6  Williams MA，Newland AC. The potential for monocyte mediated immunotherapy during infection and malignancy. Part I:apoptosis induction and cytotoxic mechanisms.Leuk Lymphoma，1999 Jun，34(1-2):1-23.    7  Becker J，Grasso RJ.Suppression of yeast ingestion by dexamethasone in macrophage cultures:evidence for a steroid-induced phagocytosis inhibitory protein.Int J Immunopharmacol 1998;10(4):325-338.    8  Grasso RJ，Klein TW.Inhibition of yeast phagocytosis and cell spreading by glucocorticoids in cultures of resident murine peritoneal macrophages.J Immunopharmacol，1981，3(2):171-192.    9  Grasso RJ， West LA.Inhibition of yeast phagocytosis by dexamethasone in macrophage cultures:reversibility of effect and enhanced suppression in cultures of stimulated macrophages.Immunpharmacol，1982-83，4(4):265-78Related.    10  Sonia L. Glucocorticoids-Induced Apoptosis in Lymphocytes.Biochemical and Biophysical Research Communications，2000，279:307-312.    11  Malech HL，Gallin JI.Current concepts:Immunology，Neutrophils in human diseases.N Engl J Med，1987，317(4):687-694.    12  Xie OW，Kastiwabara Y，Nathan CF.Role of transcription factor NF-Kb/Rel in induction of nitric oxide synthase.J Bio Chem，1996，269:4705-4710.    13  Watson RWG，Redmond HP，Wang JH，et al. Mechanisms involved in sodium arsenite-induced apoptosis of human neutrophils.J Leukoe Biol，1996，60(5):625-632.

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