NUCLEOTIDE POOLS OF NOVIKOFF RAT HEPATOMA CELLS GROWING IN SUSPENSION CULTURE .1. KINETICS OF INCORPORATION OF NUCLEOSIDES INTO NUCLEOTIDE POOLS AND POOL SIZES DURING GROWTH CYCLE
NUCLEOTIDE POOLS OF NOVIKOFF RAT HEPATOMA CELLS GROWING IN SUSPENSION CULTURE .1. KINETICS OF INCORPORATION OF NUCLEOSIDES INTO NUCLEOTIDE POOLS AND POOL SIZES DURING GROWTH CYCLE
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DOI：
10.1002/jcp.1040770212
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发表时间：
1971-01-01
影响因子：
5.6
通讯作者：
PLAGEMANN, PG
中科院分区：
文献类型：
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作者：
PLAGEMANN, PG
Novikoff肝癌细胞将3 H-5-尿苷和3 H-8-腺苷掺入酸溶性寡核苷酸和核酸的动力学研究结果（亚系N1 S1 - 67）在悬浮培养中的结果表明，尿苷转运反应在培养基中约100 μM时饱和，腺苷转运反应在培养基中约10 μM核苷时饱和，在100 μM以上，简单扩散成为两种核苷进入细胞的主要方式。转运反应的Km值，尿苷约为1.3 × 10− 5 M，腺苷约为6 × 10− 6 M。这些核苷掺入到核苷酸库和核酸中似乎受到来自核苷掺入速率的核酸合成进入速率的限制。其他复杂的因素是掺入DNA和RNA的单个核苷酸中的核苷的相对比例随标记时间的变化，细胞将尿苷分裂为尿嘧啶，腺苷脱氨生成次黄嘌呤，随后次黄嘌呤裂解生成次黄嘌呤。各种证据表明，在正常生长条件下，细胞的总核苷酸库非常小条件然而，在200 μM尿苷或腺苷存在下生长期间，细胞继续将核苷转化为细胞内核苷酸的速度比核酸合成所需的速度快得多。这导致游离尿苷和腺苷核苷酸在细胞中的积累，其最大量至少等于这些核苷酸在总细胞RNA中的量。
Results from kinetic studies on the incorporation of3H‐5‐uridine and3H‐8‐adenosine into the acid‐soluble nucleotide poor and nucleic acids by Novikoff hepatoma cells (subline N1S1‐67) in suspension culture indicate that the uridine transport reaction is saturated at about 100 μM and that for adenosine at about 10 μM nucleoside in the medium, and that above 100 μM simple diffusion becomes the predominant mode of entry of both nucleosides into the cell. The Km of the transport reactions is approximately 1.3 × 10−5M for uridine and 6 × 10−6M for adenosine. The incorporation of these nucleosides into both the nucleotide pool and into nucleic acids seems to be limited by the rate of entry of the nucleic acid synthesis from the rate of incorporation of nucleosides. Other complicating factors are a change with time of labeling in the relative proporation of nucleoside incorporated into DNA and into the individual nucleotides of RNA, the splitting of uridine to uracil by th ecells, the deamination of adenosine kto inosine and the subsequent cleavage of inosine to hypoxanthine.Various lines of evidence are presented which indicate that the overall nucleotide pools of the cells are very small under normal growth conditions. During growth in the presence of 200 μM uridine or adenosine, however, the cells continue to convert the nucleosides into intracellular nucleotides much more rapidly than required for nucleic acid synthesis. This results in an accumulation of free uridine and adenosine nucleotides in the cells, the maximum amounts of which are at least equivalent to the amount of these nucleotides in total cellular RNA.