High affinity sodium-dependent nucleobase transport in cultured renal epithelial cells (LLC-PK1).
High affinity sodium-dependent nucleobase transport in cultured renal epithelial cells (LLC-PK1).
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培养的肾上皮细胞 (LLC-PK1) 中的高亲和力钠依赖性核碱基转运。
DOI：
10.1016/s0021-9258(19)76505-3
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发表时间：
1993
期刊：
影响因子：
--
通讯作者：
S. Jarvis
中科院分区：
文献类型：
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作者：
D. Griffith;S. Jarvis
在LLC-PK 1细胞中已经表征了两种不同的核碱基转运蛋白。第一个系统在钠存在下逆着浓度梯度积累次黄嘌呤。次黄嘌呤的钠依赖性摄取在22 ℃下可饱和，Km值为0.79 +/- 0.43 μ M，Vmax为15 +/- 4 pmol/mg蛋白质/60 s，Na+：次黄嘌呤偶联化学计量为1.27 +/- 0.20。次黄嘌呤的摄取被5-氟尿嘧啶、尿嘧啶、胸腺嘧啶和鸟嘌呤抑制（Ki值3-6 μ M）。腺嘌呤和核苷没有影响。使用细胞单层上生长的可渗透的过滤器支持，Na（+）依赖性次黄嘌呤摄取发生优先从顶端表面。第二个系统没有表现出阳离子特异性，并且是可饱和的，对次黄嘌呤具有低亲和力（Km为124 +/-22 microM）和275 +/-38 pmol/mg蛋白质/60 s的高Vmax。腺嘌呤和鸟嘌呤抑制Na（+）非依赖性次黄嘌呤摄取（Ki值分别为30 +/- 15和18 +/- 7 μ M）。其他核碱基和核苷表现出很少或没有抑制平衡次黄嘌呤流入。双嘧达莫、地拉卓和根皮苷是Na（+）依赖性次黄嘌呤摄取的有效抑制剂，但对Na（+）非依赖性通量影响不大。这项研究代表了在培养的动物细胞中独特的高亲和力Na+核碱基协同转运系统的第一次直接证明。
Two distinct transporters for nucleobases have been characterized in LLC-PK1 cells. The first system accumulates hypoxanthine against a concentration gradient in the presence of sodium. The sodium-dependent uptake of hypoxanthine was saturable at 22 degrees C with a Km value of 0.79 +/- 0.43 microM, a Vmax of 15 +/- 4 pmol/mg protein/60 s, and a Na+:hypoxanthine coupling stoichiometry of 1.27 +/- 0.20. Uptake of hypoxanthine was inhibited by 5-fluorouracil, uracil, thymine, and guanine (Ki values 3-6 microM). Adenine and nucleosides were without effect. Using cell monolayers grown on a permeable filter support, Na(+)-dependent hypoxanthine uptake occurred preferentially from the apical surface. The second system exhibited no cation specificity and was saturable with a low affinity for hypoxanthine (Km of 124 +/- 22 microM) and a high Vmax of 275 +/- 38 pmol/mg protein/60 s. Adenine and guanine inhibited Na(+)-independent hypoxanthine uptake (Ki values 30 +/- 15 and 18 +/- 7 microM, respectively). Other nucleobases and nucleosides exhibited little or no inhibition of equilibrative hypoxanthine influx. Dipyridamole, dilazep, and phloridzin were effective inhibitors of Na(+)-dependent hypoxanthine uptake but had little effect on the Na(+)-independent flux. This study represents the first direct demonstration of a unique high affinity Na+ nucleobase co-transporter system in cultured animal cells.