CELL DEATH AND POLYAMINE

用鸟氨酸脱羧酶抑制剂1-氨氧基-3-氨基丙烷(AOAP)处理去多胺培养的大鼠肝癌(HTC)细胞，可引起细胞内亚精胺的异常积聚，导致细胞死亡。虽然某些形态特征提示为细胞凋亡，但在电子显微镜下观察到线粒体损伤，在凝胶电泳法分析细胞DNA时未见明显的DNA断裂，并探讨了亚精胺异常聚集的机制。结果发现，AOAP在细胞内的蓄积依赖于AOAP作用的时间，且AOAP作用时间越长，对亚精胺摄取活性的抑制作用越明显。随着AOAP暴露时间的延长，蛋白质合成速率下降到对照的20%，这表明AOAP长期暴露于抑制亚精胺摄取活性所需的细胞中，从而抑制蛋白质的合成，从而导致亚精胺的异常积累。为了开发一种能够将过量的多胺引入细胞的前药，合成并检测了多胺的二乙酰衍生物。研究发现，双乙酰五胺是多胺摄取系统和多胺氧化酶的良好底物，在HTC细胞中可有效地转化为亚精胺或去甲精胺。但这些化合物没有被成功地带入细胞内，达到异常的积累水平，这表明没有利用多胺转运系统的结构是化合物在细胞内积累到过量水平所必需的。

It was found that administration of spermidine to cultured rat hepatoma (HTC) cells depleted of polyamine with ornithine decarboxylase inhibitor, 1-aminooxy-3-aminopropane (AOAP), 1ed to an abnormal accumulation of cellular spermidine followed by the cell death. although, some morphorogical features suggested it was apoptosis, mitocondrial damage was observed in electron micrograph and a clear fragmentation of DNA was not observed in the analysis of cellular DNA by gel electrophoresis.Mechanism of tha abnormal accumulation of spermidine was examined. It was found that the accumulation was dependent on the exposure period of AOAP to the cells, and that the longer exposure of AOAP inhibited repression of spermidine uptake activity. As protein synthesis rate was decreased to 20% of control by the longer exposue of AOAP,it was suggested that inhibition of synthesis of a protein by the long exposure of AOAP to the cells which was needed in the repression of spermidine uptake activity led to the abnormal accumulation of spermidine.In order to develope a prodrug which enable us to introduce excess polyamine into cells diacetly derivatives of polyamine were synthesized and examined. It was found that diacetyl pentaamines were good substrates of polyamine uptake system and polyamine oxidase, and then efficiently converted into spermidine or norspermidine in HTC cells. But these compounds were not successfully taken into the cells to an abnormal accumulation level, suggesting that the srtucture which does not utilize polyamine transport system is needed for the compound to be accumulate to excess level in cells.