Expression of a human renal sodium nucleoside cotransporter in Xenopus laevis oocytes.
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.
Gutierrez
M M
MM
School of Pharmacy, University of California, San Francisco 94143.
Giacomini
K M
KM
D000818:Animals; D002352:Carrier Proteins / Q000235:genetics*; D015870:Gene Expression; D006801:Humans; D007668:Kidney / Q000378:metabolism*; D007700:Kinetics; D009705:Nucleosides / Q000378:metabolism; D009865:Oocytes / Q000378:metabolism*; D012333:RNA, Messenger / Q000494:pharmacology; D012964:Sodium / Q000378:metabolism; D027981:Symporters; D014162:Transfection; D014982:Xenopus laevis
D002352:Carrier Proteins; D009705:Nucleosides; D012333:RNA, Messenger; D027981:Symporters; C073034:sodium-nucleoside cotransporter; D012964:Sodium