Fig. 5.

Inhibition of [³H]uridine uptake in HeLa cells by endogenous nucleosides. IC₅₀ analysis of adenosine (A), guanosine (B), and thymidine (C), inosine (D), and cytidine (E). Total [³H]uridine uptake (black open circle), ENT1-mediated [³H]uridine uptake (blue diamond), and ENT2-mediated [³H]uridine uptake (red triangle) were measured in the presence of endogenous nucleosides. ENT2 mediated uptake was taken as that occurring in the presence of 100 nM NBMPR. ENT1 data points were determined by subtracting calculated ENT2 uptake from total uptake and fitting the data to a single component IC₅₀ equation. Best-fit lines were created to determine relevant values using GraphPad Prism 7. Increasing concentrations of each compound were incubated with approximately 20 nM [³H]uridine or 20 nM [³H]uridine and 100 nM NBMPR. Data points in the graph are reported as mean ± S.D. of triplicate values (n = 3).