Transport energetics of the folic acid analogue, methotrexate, in L1210 leukemia cells. Enhanced accumulation by metabolic inhibitors.
Transport energetics of the folic acid analogue, methotrexate, in L1210 leukemia cells. Enhanced accumulation by metabolic inhibitors.
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叶酸类似物甲氨蝶呤在 L1210 白血病细胞中的转运能量学。
DOI：
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发表时间：
1969
影响因子：
4.8
通讯作者：
I. Goldman
中科院分区：
文献类型：
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作者：
I. Goldman
本文研究了叶酸类似物甲氨蝶呤在小鼠白血病细胞L1210中的能量依赖性转运。发现许多代谢抑制剂可增强甲氨蝶呤的单向流入和蓄积。用叠氮化钠详细研究了这种现象。叠氮诱导的甲氨蝶呤单向流入增加与最大转运速度和流入米氏常数的升高有关。叠氮化物对内流的影响与甲氨蝶呤被动扩散的增加无关。研究发现，在存在和不存在叠氮化合物的情况下，添加丙酮酸（叠氮化合物抑制的代谢过程的能量底物）可以抑制甲氨蝶呤的流入。叠氮化物可减慢甲氨蝶呤的单向外排。在叠氮化物存在下，从装载高水平甲氨蝶呤的细胞的流出是一个双组分过程，其中细胞内甲氨蝶呤的主要部分以缓慢和恒定的速度离开。数据表明，叠氮化物降低了单向外排过程的最大传输速度和米氏常数。在不存在叠氮化物的情况下，细胞内甲氨蝶呤的电化学电势超过细胞外甲氨蝶呤的电化学电势。数据表明，叠氮化物进一步增加了这种电化学电势差。因此，这些研究表明，在L1210白血病细胞中叠氮化物的存在下，甲氨蝶呤的能量依赖性转运增强。
Abstract Energy-dependent transport of the folic acid analogue, methotrexate, was studied in L1210 murine leukemia cells. A number of metabolic inhibitors were found to enhance the unidirectional influx and accumulation of methotrexate. This phenomenon was studied in detail with sodium azide. The azide-induced increase in the unidirectional influx of methotrexate was associated with a rise in both the maximum transport velocity and the influx Michaelis constant. The effect of azide on influx was not related to an increase in the passive diffusion of methotrexate. Addition of pyruvate, an energy substrate for those metabolic processes inhibited by azide, was found to depress methotrexate influx in the presence and absence of azide. The unidirectional efflux of methotrexate was slowed by azide. Efflux from cells loaded to high levels of methotrexate in the presence of azide was a two-component process with the major part of intracellular methotrexate exiting at a slow and constant velocity. The data suggested that azide reduces the maximum transport velocity and the Michaelis constant for the unidirectional efflux process. In the absence of azide the electrochemical potential for intracellular methotrexate exceeds that for extracellular methotrexate. The data indicate that azide further increases this electrochemical potential difference. These studies therefore suggest that energy-dependent transport of methotrexate is enhanced in the presence of azide in the L1210 leukemia cell.