Studies on the uptake of [3H]dopamine by synaptic vesicle fraction isolated from bovine brain.
1. A synaptic vesicle fraction isolated from bovine caudatolenticular nuclei showed enzymic activities of tyrosine hydroxylase [EC 1.14.16.2] and dopamine beta-hydroxylase [EC 1.14.17.1]. Tyrosine hydroxylase, whose subcellular localization is uncertain, appeared to be associated with the synaptic vesicles. 2. The vesicle fraction took up [3H]dopamine increasingly with time without the aid of ATP (6.3 pmol of [3H]dopamine per mg of vesicle proteins, or 3-4% of the added dopamine, at 30 min). In the presence of ATP, a transient accumulation of the amine was observed, reaching the highest level at 7-10 min (5.6 pmol dopamine/mg protein), and then a rapid release of the amine took place, obeying first-order kinetics with respect to the amine concentration. The amine uptake was strongly inhibited with NEM, regardless of the presence or absence of ATP. 3. The vesicle fraction also exhibited a weak ability to translocate protons inward and ATP-dependently, as monitored by an increase in the fluorescence intensity of ANS. The fluorescence enhancement persisted for at least 30 min and this time-dependent change was not consistent with that of the transient accumulation of [3H]dopamine mentioned above. Since the present vesicle preparation contained a small amount of mitochondrial ATPase (18-20% of the total activity), the proton translocating ability could be attributable to contaminating submitochondrial particles. 4. Therefore these results made it impossible to conclude that the transient uptake of [3H]dopamine by the synaptic vesicles was coupled to ATP hydrolysis.
D000244:Adenosine Diphosphate / Q000494:pharmacology; D000251:Adenosine Triphosphatases / Q000378:metabolism; D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D001921:Brain / Q000378:metabolism*; D017301:Ca(2+) Mg(2+)-ATPase; D002417:Cattle; D004140:Dinitrophenols / Q000494:pharmacology; D004298:Dopamine / Q000378:metabolism*; D004299:Dopamine beta-Hydroxylase / Q000378:metabolism; D005033:Ethylmaleimide / Q000494:pharmacology; D006639:Histidine / Q000494:pharmacology; D007700:Kinetics; D009840:Oligomycins / Q000494:pharmacology; D013572:Synaptic Vesicles / Q000378:metabolism*; D014316:Tritium; D014446:Tyrosine 3-Monooxygenase / Q000378:metabolism
D004140:Dinitrophenols; D009840:Oligomycins; D014316:Tritium; D006639:Histidine; D000244:Adenosine Diphosphate; D014446:Tyrosine 3-Monooxygenase; D004299:Dopamine beta-Hydroxylase; D000251:Adenosine Triphosphatases; D017301:Ca(2+) Mg(2+)-ATPase; D005033:Ethylmaleimide; D004298:Dopamine