Fig. 7. Zinc increases in vitro vesicular glutamate uptake. (A) SLMV-enriched fractions were prepared from untransfected (wt) and Vglut1-transfected (Vgl) cells. Vesicle-specific [³H]-glutamate uptake was determined in either the absence or the presence of the ionophore valinomycin (20 µM). Vesicular glutamate uptake is detected only in SLMV fractions from Vglut1-transfected cells (n=2). (B) [³H]-Glutamate uptake was performed in either the absence or the presence of increasing concentrations of ionic zinc (ZnSO₄). Equal amounts of Vgl and VglZn6 SLMV protein were used in all assays. The protein content per assay was confirmed by immunoblot using antibodies against synaptic-vesicle markers.