SLC28A1 encodes CNT1 (concentrative nucleoside transporter-1), a sodium-dependent symporter that mediates pyrimidine nucleoside uptake 1. CNT1 specifically transports uridine, cytidine, and thymidine across the plasma membrane by coupling their transport to the transmembrane sodium gradient, also transporting adenosine with high affinity but lower velocity 2. The protein localizes primarily to epithelial tissues, including renal brush border membranes where it participates in nucleoside reabsorption 3. CNT1 plays critical roles in nucleoside salvage pathways and adenosine signaling termination 1. As a key determinant of nucleoside analog disposition, CNT1 significantly influences the pharmacokinetics and efficacy of anticancer and antiviral nucleoside drugs 2. CNT1 expression is transcriptionally regulated by hepatocyte nuclear factor-4alpha and suppressed by bile acids 4. Loss-of-function mutations in SLC28A1 cause uridine-cytidineuria, a rare pyrimidineuria with unclear clinical consequences 5. Notably, SLC28A1 knockout provides cardioprotection against doxorubicin-induced cardiotoxicity in human cardiomyocytes 6, suggesting CNT1-mediated drug uptake contributes to anthracycline toxicity. Additionally, SLC28A1 variants influence metformin response in diabetes treatment 7.