LLC-PK1 renal cells show Na+-dependent and Na+-independent hypoxanthine uptake. While the latter is inhibited by adenine, neither are inhibited by xanthine. In rats, intestinal Na+-dependent hypoxanthine transporter Slc23a4 is not expressed in the kidney, and its action is inhibited by xanthine. This study aimed to clone Slc23a4-paralog SLC23A3 from the human kidney and investigate its hypoxanthine transport activity. We observed Na+-dependent 10 nM [3H]-hypoxanthine uptake in SLC23A3 RNA-injected Xenopus oocytes. Moreover, 100 μM xanthine did not inhibit Na+-independent 300 nM [3H]-hypoxanthine uptake, whereas 100 μM adenine did. These results confirm that SLC23A3 is a hypoxanthine transporter in the human kidney.
Keywords: Hypoxanthine; adenine; nucleobase transporter; xanthine.