FIG. 2.

Uptake of [³H]pentamidine by the tbat1-null mutant. The uptake of 15 nM [³H]pentamidine was unaffected by as much as 1 mM adenosine (filled circles) but was inhibited to a maximum of 64% by propamidine (open squares), with an IC₅₀ of 6.5 μM. When increasing amounts of unlabeled pentamidine (filled squares) were added, [³H]pentamidine uptake was inhibited in a biphasic manner (P < 0.0001 by the F test), with the high-affinity component (IC₅₀ = 25.1 nM) contributing 62% of total [³H] pentamidine transport. The IC₅₀ of the low-affinity component was 19.5 μM for this experiment.