摘要或動機

儘管鍺在電子工業上被廣泛運用，但對於暴露在鍺化合物所產生的毒害則尚未被詳細的探討。在探討鍺對細胞所產生的生理影響中，我們使用了二氧化鍺 ( GeO₂）和有機鍺（
Ge-132 ）。由實驗結果顯示， GeO₂，會造成人類子宮上皮癌細胞（ A 431 ) 及巨噬細胞株（ Raw264.7 ）死亡，而 Ge -132 對細胞生長則不造成任何影響，為了進一步了解鍺引起細胞死亡是否是經過細胞凋亡（apoptosis
) ，我們將鍺處理過的細胞進行染色體 D NA 的分析，結果發現細胞中 DNA 染色體沒有斷裂。由先前 Huang 等人於 1999 年的研究結果顯示，砷對細胞所造成的毒性是經由有絲分裂活化酵素（
MAPK ）傳導路徑，所以為了解鍺誘導細胞死亡的路徑，我們亦分析 MAPK 傳導路徑是否亦參與其中，我們發現 GeO₂加入 A431 細胞後，會活化有絲分裂活化酵素中的
ERK ，但對JNK 及 p38 皆無影響，在對蛋白質表現方面，轉錄因子 c-Jun 的蛋白質表現也是隨著GeO₂加入的時間增加而上升。 GeO₂加入 Raw
264 . 7cell 後，會造成 JNK 、 ERK 的活化，同樣的轉錄因子 c- Jun 也會增加，由此一結果得知鍺對細胞的影響會因細胞的不同而有所差異，為了分析自由基是否參與砷及鍺所造成細胞死亡的過程，我們分析在
A431 細胞中可產生的 NO 的可誘導性 nitric oxide synthase ( iNOS ）的表現，我們發現氧化鍺及砷都會誘導 iNOS 的表現量增加。綜合以上結果，可能顯示氧化錯可能會經由
M A PK 訊息傳遞路徑來促使細胞的死亡，並且 iNOS 亦可能參與此過程。就我們所知，這是第一個提出重金屬所造成的毒害可能會經由 iNOS 來誘導產生的研究。

Despite the extensive use of germanium (Ge) in the electronic industry and optical
devices, the potential risks of exposure to germanium compounds have not been evaluated.
The effects of germanium on cell physiological functions were studied. We first
asked if germanium oxide (GeO₂) or carboxyethylgermanium (Ge-l32) could affect cell
viability. We found that GeO₂, but not Ge-l32, reduced cell viability in a dose-dependent
manner in epidermoid carcinoma A43 I and macrophage Raw 264.7 cells. In order to
test whether apoptosis contributes to germanium cytotoxicity, DNA fragmentation
was evaluated in A43 1 and Raw 264.7 cells treated with GeO₂ or Ge-132, respectively.
We found that neither GeO₂ nor Ge- 132 had effect on chromosomal DNA fragmentation.
Previous studies by Huang (1999) et al indicated that sodium arsenite (NaAsO₂) cytotoxicity
is mediated through mitogen-activated protein kinase (MAPK) pathways. In order to
study the mechanism(s) by which GeO₂ mediates cell death, we analyzed the signal
transduction pathways triggered by GeO₂ We found that GeO₂ stimulated the extracellular
signal-regulated kinase (ERK) activity and transcription factor c-Jun in a time-dependent
manner, but not c-Jun amino-terminal kinasc (JNK), or p38 MAPK in A431 cells. Treatment
of the Raw 264.7 cells with GeO₂, induced activities of ERK, JNK and c-Jun in a
time-dependent manner. Collectively, these results suggested that GeO₂ effects might
be cell type specific. To test whether free radicals were involved in NaAsO₂ or
GeO₂ mediated cell death, the expression of inducible nitric oxide synthase (iNOS),
which produced the NO free radical, was determined in A431 cells treated with NaAsO₂
or GeO₂. We found that expression of iNOS was induced in a time-dependent manner
in NaAsO₂ or GeO₂-treted A431 cells. Taken together, our results indicated that
GeO₂-induccd cell death may be mediated through MAPK signal pathways and that iNOS
may contribute to NaAsO₂ or GeO₂ mediated cell death. To our knowledge, this is
the first report that iNOS may contribute to heavy metal mediated cytotoxicity.