| Summary: | 碩士 === 台北醫學院 === 醫學研究所 === 88 === Epidemiological evidence suggested that cadmium (Cd) and mercury (Hg) exposure might cause pulmonary damage. However, the mechanisms were not clear yet. Cd or Hg had been reported to induce apoptosis in some cell lines and might correlate with redox signaling. In our research, a normal human fetal lung fibroblast cell line (MRC-5) was used as a cell model to investigate the effects of reactive oxygen species (ROS) during apoptosis triggered by Cd or Hg. Among numerous antioxidant compounds or enzymes, N- acetylcysteine (NAC)、pyrrolidine dithiocarbamate (PDTC)、ascorbic acid、selenium (Se)、tiron、mannitol、catalase and SOD, NAC and PDTC would suppress the Cd-induced cytotoxicity efficiently and the .O2- scavenger, tiron, showed partial protective ability. NAC and tiron also exhibited partial protective ability of Hg-induced cytotoxicity in MRC-5 cell. By flow cytometric analysis with propidium iodide (PI) staining, the sub-G1 content was raised from basal level to 66 % or 11 % after treatment with Cd or Hg, respectively. These results indicated that the cytotoxicity of Cd might mediate MRC-5 cells to apoptosis. To monitor the generation of ROS after treatment of Cd or Hg, 2’,7’- dichlorodihydrofluorescein diacetate (DCFH-DA), dihydroethidium (HEt) and dihydrorhodamine 123 (DHR123) were used to detect H2O2, .O2- and mitochondrial H2O2, respectively. Three-fold (Cd treatment) and twenty- fold (Hg treatment) elevation of H2O2 were detected. Nevertheless, only three-fold of .O2-.was increased by Hg treatment, but there was no any effect after Cd treatment. On the other hand, the mitochondrial H2O2 was decreased half after Hg treatment, but no change after treatment with Cd. These findings indicated that ROS might play pivotal roles during apoptosis and cytotoxicity induced by Cd, and partial participated in Hg-induced cytotoxicity..
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