Gutierrez M M, Giacomini K M
School of Pharmacy, University of California, San Francisco 94143.
Biochem Pharmacol. 1994 Dec 16;48(12):2251-3. doi: 10.1016/0006-2952(94)00411-0.
In this study, Xenopus laevis oocytes injected with poly(A)+ RNA (mRNA) isolated from human kidney were used to express a Na(+)-nucleoside cotransporter. Na(+)-stimulated [3H]thymidine uptake was enhanced 2-3-fold in oocytes injected with 50 ng poly(A)+ RNA and 4-5-fold in oocytes injected with 20 ng of a size-fractionated human renal cortex mRNA fragment (2-3 kb) in comparison with water-injected oocytes. Na(+)-dependent thymidine uptake in oocytes injected with the 2-3 kb mRNA fragment was inhibited significantly by thymidine and guanosine but not by formycin B, consistent with the N4 Na(+)-nucleoside cotransporter. The Km (28 microM) of Na(+)-dependent thymidine uptake in the oocytes injected with the 2-3 kb mRNA fragment was similar to the Km (27 microM) of Na(+)-dependent thymidine uptake obtained in human renal brush border membrane vesicles. These data suggest for the first time that a Na(+)-nucleoside cotransporter from human kidney can be expressed in X. laevis oocytes.
在本研究中，将注射了从人肾中分离出的聚腺苷酸加尾RNA（mRNA）的非洲爪蟾卵母细胞用于表达一种钠-核苷共转运体。与注射水的卵母细胞相比，注射50 ng聚腺苷酸加尾RNA的卵母细胞中，钠刺激的[3H]胸苷摄取增强了2至3倍，而注射20 ng大小分级的人肾皮质mRNA片段（2至3 kb）的卵母细胞中，该摄取增强了4至5倍。注射2至3 kb mRNA片段的卵母细胞中，钠依赖性胸苷摄取受到胸苷和鸟苷的显著抑制，但不受间型霉素B的抑制，这与N4钠-核苷共转运体一致。注射2至3 kb mRNA片段的卵母细胞中，钠依赖性胸苷摄取的Km（28 μM）与人肾刷状缘膜囊泡中钠依赖性胸苷摄取的Km（27 μM）相似。这些数据首次表明，人肾中的一种钠-核苷共转运体可以在非洲爪蟾卵母细胞中表达。
