Nucleoside transport in human and sheep erythrocytes. Evidence that nitrobenzylthioinosine binds specifically to functional nucleoside-transport sites.
Nucleoside transport in human and sheep erythrocytes. Evidence that nitrobenzylthioinosine binds specifically to functional nucleoside-transport sites.
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人和羊红细胞中的核苷转运。
作者：
S. Jarvis;J. Young
硝基苄基[35 S]硫代肌苷结合和硝基[3 H]苄基硫代肌苷结合核苷可渗透和核苷不可渗透的绵羊红细胞膜进行了研究，并与人红细胞的发现进行了比较。高亲和力硝基苄硫代肌苷结合位点（表观KD等于1 nM）存在于人和核苷可渗透但核苷不可渗透的绵羊红细胞膜上（人和绵羊核苷可渗透的绵羊红细胞的8400和18个位点/细胞被硝基苄硫代鸟苷和双嘧达莫取代。尿苷、肌苷和腺苷抑制结合。与人红细胞相比，核苷渗透性细胞上的硝基苄基硫代肌苷位点的数量较少，对应于相当低的Vmax。对于这些细胞中的尿苷内流（25 ℃时为0.53 × 10（-20）mol/细胞每秒，相比之下为254 × 10（-20）mol/细胞每秒）。有人建议，高亲和力nitrobenzylthiosine结合代表了一个特定的相互作用与功能核苷转运位点。对于核苷可渗透的绵羊细胞和人红细胞，25 ℃下每个转运位点的尿苷转运能力为180个分子/位点/s（假设硝基苄基硫代肌苷与核苷转运系统之间的相互作用为1：1）。
Nitrobenzyl[35S]thioinosine binding and nitro[3H]benzylthioinosine binding to nucleoside-permeable and nucleoside-impermeable sheep erythrocyte membranes was investigated, and compared with that found for human erythrocytes. High-affinity nitrobenzylthioinosine-binding sites (apparent KD congruent to 1 nM) were present on human and nucleoside-permeable but not nucleoside-impermeable sheep erythrocyte membranes (8400 and 18 sites/cell for human and sheep nucleoside-permeable sheep erythrocytes was displaced by nitrobenzylthioguanosine and dipyridamole. Uridine, inosine and adenosine inhibited binding. The smaller number of nitrobenzylthioinosine sites on nucleoside-permeable cells compared with human erythrocytes corresponded to a considerably lower Vmax. for uridine influx in these cells (0.53 X 10(-20) mol/cell per s at 25 degrees C compared with 254 X 10(-20) mol/cell per s). It is suggested that high-affinity nitrobenzylthioinosine binding represents a specific interaction with functional nucleoside-transport sites. The uridine-translocation capacity for each transport site at 25 degrees C is 180 molecules/site per s for both nucleoside-permeable sheep cells and human erythrocytes (assuming a 1:1 interaction between nitrobenzylthioinosine and the nucleoside-transport system).