Characteristics of folic acid transport in the L1210 leukemia cell.
Characteristics of folic acid transport in the L1210 leukemia cell.
复制标题
L1210白血病细胞中叶酸转运的特征。
DOI：
10.1016/0005-2736(69)90204-1
复制
发表时间：
1969
期刊：
影响因子：
--
通讯作者：
I. Goldman
中科院分区：
文献类型：
--
作者：
N. Lichtenstein;V. Oliverio;I. Goldman
本文研究了L1210白血病细胞对叶酸的摄取。叶酸在该细胞系统中迅速代谢，代谢产物似乎可以通过细胞膜进行交换。用氨甲喋呤(4-氨基-4-DOX-10-甲基蝶酰谷氨酸)抑制二氢叶酸还原酶可部分抑制细胞的代谢。研究了细胞叶酸转运的能量依赖性。这些研究表明，叶酸的外排机制是能量依赖的，因为(1)细胞内和胞外的叶酸在稳态时的比值远低于被动平衡转运系统的预测；(2)抑制能量代谢导致叶酸的单向外流减少，净摄取速度显著增加。尽管叶酸的残留代谢使数据的解释变得复杂，但对叶酸的许多研究结果与观察到的甲氨蝶呤相似--甲氨蝶呤是一种化合物，其转运机制至少部分与叶酸相同，在这些实验的条件下不被代谢。与主动外排机制相一致的是，观察到[~3H]叶酸的净摄取是一个复杂的过程，在将叶酸加入细胞外介质后30秒内，标记的反流变得显著，细胞叶酸水平远远低于稳定状态。随后，在观察期的剩余时间内，净摄取速率减慢至基本恒定的速度，代表着大得多的单向流入和流出速率之间的非常小的差异。净摄取高度依赖于温度(Q10of5)，并且显著地被甲氨蝶呤和叶酸抑制。在摄取叶酸的过程中，将这些物质添加到细胞外介质中，会导致几乎所有细胞内标记的净外流。
Uptake of folic acid was studied in L1210 leukemia cells. Folic acid was rapidly metabolized in this cell system and the metabolites appeared to be exchangeable across the cell membrane. Metabolism was partially reduced when cells were pretreated with methotrexate (4-amino-4-doxy-10-methylpteroylglutamic acid) to inhibit dihydrofolate reductase.The energy dependence of folic acid transport was investigated in cells pretreated with methotrexate to minimize metabolism. These studies suggested an energy-dependent efflux mechanisms for folic acid, since (1) the ratio of intracellular to extracellular folic acid at the steady state was far below that predicted for a passive equilibrating transport system and (2) inhibition of energy metabolism resulted in a decrease in the unidirectional efflux of folic acid and a marked rise in the net uptake velocity. Although interpretation of the data is complicated by residual metabolism of folic acid, many of the findings for folic acid are similar to those observed for methotrexate—a compound which shares, at least in part, the same transport mechanism as folic acid and is not metabolized under the conditions of these experiments.Compatible with an active efflux mechanism was the observation that net uptake of [3H]folic acid is a complex process in which back flux of label becomes significant within 30 sec after the addition of folic acid to the extracellular medium and at cell folate levels far below the steady state. Following this, the rate slows to an essentially constant velocity for the remainder of the period of observation and represents a very small difference between much larger unidirectional influx and efflux rates.Net uptake is highly temperature dependent (Q10of 5) and is markedly inhibited by methotrexate and folinic acid. Addition of these substances to the extracellular medium during uptake of folic acid results in net efflux of essentially all intracellular label.