Inhibition of uridine uptake in HeLa cells by nitrobenzylthioinosine and related compounds.
Inhibition of uridine uptake in HeLa cells by nitrobenzylthioinosine and related compounds.
复制标题
硝基苄基硫代肌苷和相关化合物抑制 HeLa 细胞中尿苷的摄取。
作者：
A. Paterson;S. R. Naik;C. Cass
HeLa细胞单层培养物在20°下的尿苷摄取速率在几分钟内是恒定的，并且速率饱和性是明显的。硝基苄基硫代肌苷（NBMPR），一个有效的核苷转运抑制剂，废除饱和摄取尿苷，揭示了一个非饱和的吸收，显然是由于简单的扩散组件。在摄取试验条件下，尿苷的主要代谢产物为UTP。NBMPR对HeLa细胞提取物中的尿苷激酶或完整细胞中尿苷拮抗剂的相对比例没有影响。这些结果表明NBMPR抑制尿苷进入细胞的介导通道。NBMPR对尿苷转运的抑制的特征在于Vmax值不变，表观Km值增加，无论是在摄取测定中同时加入抑制剂和渗透剂还是细胞先前已用抑制剂处理。为了评估抑制活性的结构要求，测试了结构上与NBMPR相关的化合物抑制尿苷摄取的能力;其中，最有效的是NBMPR的29-脱氧核糖基和阿拉伯糖基类似物以及6-硫代鸟苷、29-脱氧-6-硫代鸟苷和6-硒代鸟苷的S6-硝基苄基衍生物。
Rates of uridine uptake by logarithmically proliferating monolayer cultures of HeLa cells at 20° were constant for intervals of several minutes, and rate saturability was evident. Nitrobenzylthioinosine (NBMPR), a potent inhibitor of nucleoside transport, abolished saturable uptake of uridine, revealing a nonsaturable component of uptake that apparently was due to simple diffusion. Under conditions of the uptake assay, the principal metabolite of uridine was UTP. NBMPR had no effect on uridine kinase in HeLa cell extracts, or on the relative proportions of uridine anabolites in intact cells. These results indicate that NBMPR inhibited mediated passage of uridine into the cell. The inhibition of uridine transport by NBMPR was characterized by unchanged Vmax values, with increases in apparent Km values, whether the inhibitor and permeant were added simultaneously in the uptake assay or the cells had previously been treated with inhibitor. To assess the structural requirements for inhibitory activity, compounds related structurally to NBMPR were tested for their ability to inhibit uridine uptake; of these, the most effective were the 29-deoxyribosyl and arabinosyl analogues of NBMPR and the S6-nitrobenzyl derivatives of 6-thioguanosine, 29-deoxy-6-thioguanosine, and 6-selenoguanosine.