| Summary: | 碩士 === 國立成功大學 === 化學系碩博士班 === 96 === Chromium (Cr) has been widely used in industries because of its high melting point, hardness, and corrosion-resistant. Hexavalent chromium (Cr6+) has been considered with strong biotoxicity.
It is documented that Cr6+ could generate reactive oxygene species (ROS) to cause interior damages for bioorganisms. In many reports ROS has been associated with mitochondria DNA (mtDNA) alterations (including ΔmtDNA4977 and mtDNA copy number). The relationship between mtDNA alterations and Cr6+ exposure, however, has not been postulated yet. The purpose of this study was to investigate the association of ΔmtDNA4977 and mtDNA copy number with samples that exposed to Cr6+. 13 workers occupationally exposed to high levels of Cr6+and 13 age, seniority, drinking and smoking matched low-exposed workers were monitored on their urinary chromium concentrations by graphite atomic absorption spectrophotometer. We found the frequencies of relative ΔmtDNA4977 in high Cr6+ exposure group were significantly higher than those in the low Cr6+ exposure group (p＝0.020). On the other hand, the mtDNA copy number in high Cr6+ exposure group were marginally lower than those in the low Cr6+ exposure group (p＝0.054). We concluded that long-term exposure to hexavalent chromium could cause mitochondria alterations. Further study with more subjects involved is warranted.
Alternately, animal experiments were also conducted to study the relationships between the concentration of ROS and mitochondria membrane potential. Twenty-five male rats of 8-12 weeks old Sprague-Dawley were exposed to potassium dichromate by intraperitoneal. Sacrificing and quarrying their blood, urine and sperm samples after exposing for fourteen days of different concentrations of Cr6+. According to the increasing exposure concentration, the results of the membrane potential showed the same tendency, but in DNA lesion and ROS concentration were not have this trend. Relatively, the human samples show the significant correlation to exposure concentration. It might due to first, the fourteen days exposure period of animal study is too short to cause significant response to exposure concentration, and secondly sample size insufficient to lead to the fact of this phenomenon too. Further study with more subjects involved and long exposure time is warranted.
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