Nucleoside triphosphate and cation requirement for dopamine uptake by plain synaptic vesicles isolated from rat cerebrums

Measurement of kinetically resolved vesicular dopamine uptake and efflux using rotating disk electrode voltammetry

“…Vesicular DA uptake was strongly temperature-dependent with uptake occurring readily at 37 • C and no detectable uptake occurring at 30 • C. Previous studies using [ 3 H] labeled compounds have also shown temperature-dependent uptake of DA and other substrates in vesicular preparations (Del Zompo et al, 1993;Seidler et al, 1977;Tanaka et al, 1976). However, these earlier studies all showed measurable vesicular uptake occurring at 30 • C and lower temperatures while the current study does not.…”

Uptake of Catecholamines by Storage Vesicles

“…uptake into only dopaminergic vesicles with [3H)dopamine, or uptake into only 5-hydroxytryptaminergic vesicles with [3H]5-HT is clearly incorrect (39,59,61), Two approaches have been taken to resolve the question o f specificity o f types o f vesicles obtained from the brain: use of brain regions specifically rich in one type of transmitter, and use o f neurotoxic agents specific to certain neuron populations. Attempts at extensive puri fication o f an individual vesicle type, using density gradient ultracentrifugation in combina tion with membrane ultrafiltration, have been partially successful in identifying biogenic amine uptake, storage and energy requirement characteristics (65,67,68). Unfortunately, some degradation o f vesicle properties may occur during purification procedures, as evi denced by substantial loss of endogenous amine content (15) and by a 10-fold increase in the transport Km in purified vesicles compared to crude preparations (46,59,65,67).…”

“…Attempts at extensive puri fication o f an individual vesicle type, using density gradient ultracentrifugation in combina tion with membrane ultrafiltration, have been partially successful in identifying biogenic amine uptake, storage and energy requirement characteristics (65,67,68). Unfortunately, some degradation o f vesicle properties may occur during purification procedures, as evi denced by substantial loss of endogenous amine content (15) and by a 10-fold increase in the transport Km in purified vesicles compared to crude preparations (46,59,65,67). Crude vesicles prepared from brain regions o f the pig (39 41), display few differences among various biogenic amine vesicle types; subsequent re ports in rat whole brain and brain regions (46,59,61,62) indicate that dopaminergic and noradrenergic vesicles have identical uptake properties.…”

Binding and immobilization of catecholamines by liposomes

“…orders of magnitude larger than the apparent KM values reported for active uptake processes. Catecholamines have KM values of 10-7-10-6 M for uptake by synaptosomes [21], and the KM for dopamine uptake by plain synaptic vesicles is 1.6 pM [22] . The specific high affinity binding of dopamine to calf striatal membranes is half saturated at 7 nM [23] .…”