FIG. 1.

Uptake of [³H]adenosine by the tbat1-null mutant. Uptake of 20 nM [³H]adenosine was inhibited by inosine (filled squares) with an IC₅₀ of 1.1 ± 0.1 μM. Adenine failed to inhibit [³H]adenosine at concentrations as high as 100 μM when it was added alone (open squares). The inhibition induced by 1 mM adenine is attributable to a low-affinity inhibition of P1.