Figure 3.

Transport measurements in digitonin permeabilized SLC10A4-HEK293 and VMAT2-HEK293 cells. Prior to transport measurements, stably transfected human SLC10A4-HEK293 cells and human VMAT2-HEK293 cells were pre-incubated with 15 µM digitonin for 10 min for permeabilization. Then the uptake of 400 nM [³H]serotonin, [³H]norepinephrine, or [³H]dopamine was measured over 10 min in the presence and absence of 5 mM ATP in the transport buffer. In addition to ATP, 2 µM of the potent VMAT2 inhibitor tetrabenazine (TBZ) or 5 µM of the proton ionophore carbonylcyanide-p-trifluoromethoxyphenylhydrazon (FCCP) were added to the transport buffer as indicated. After 10 min, the cells were washed with ice-cold PBS, lysed, and subjected to scintillation counting. The values represent mean ± SD of one representative experiment (for dopamine, n = 4) or two independent experiments (for serotonin and norepinephrine, n = 8). *Significantly different from control with p < 0.05. ^#Significantly different from positive uptake, p < 0.05.