Figure 5.

Specificity of the inhibitory effect produced by IPF α. Bovine synaptic vesicles (50 μg of protein) were suspended in the glutamate uptake assay medium as described in the text. Bovine synaptosomes (35 μg of protein) were suspended in 0.12 ml of Krebs-Ringer solution containing 1 mM spermine and 1 μM [³H]glutamate (1.67 Ci/mmol) in the presence of Na⁺ (150 mM) or choline (150 mM). Bovine chromaffin vesicles (45 μg of protein) were suspended in 0.12 ml of a solution containing 0.3 M sucrose, 1 mM spermine, 10 mM MgSO₄, 5 mM ATP, 10 mM Hepes (pH 7.0), and 50 μM [³H]norepinephrine (0.017 Ci/mmol) with or without 1 μM reserpine. Each membrane mixture also contained either 0, 26, or 100 nM IPF α. Glutamate uptake was allowed to proceed for 10 min at 30°C and 30 min at 37°C for norepinephrine uptake. Reaction was terminated by filtration as described in in the text. Values for the percentage of control were calculated relative to the specific uptake activity obtained in the absence of IPF α. Uptake into synaptic vesicles is represented by ATP-dependent uptake, that into synaptosomes by Na⁺-dependent uptake and that into chromaffin vesicles by reserpine-sensitive uptake.