title: 3H-dopamine accumulation by rat brain synaptic vesicles in a membrane-impermeable medium.
abstract: 3H-Dopamine (DA) accumulation by storage vesicles from whole rat brain was significantly stablized in a buffer system based upon the membrane-impermeant D-potassium tartrate. 3H-DA uptake saturated by twenty minutes (Km 2.1 X 10(-5)M) and remained stable for periods of 40-60 minutes. Accumulated DA was rapidly exchangeable with exogenous DA. Total levels of accumulation (pmol/mg protein) were 41.7 +/- 2.9 (37 degrees), 11.9 +/- 2.5 (4 degrees), 31.3 +/- 1.8 (absence of ATP), 26.3 +/- 2.7 (reserpine, 10(-6)M), 26.1 +/- 0.67 (no ATP + reserpine 10(-6), and 14.6 +/- 2.4 (carbonylcyanide-p-triflouromethoxyphenylhydrazone, FCCP, 10(-6)M). Depletion of endogenous DA levels by pretreatment of the animals with alpha-methyl-p-tyrosine greatly diminished the reserpine-insensitive DA accumulation. After depletion of endogenous DA, ATP-independent uptake was significantly retarded, but eventually reached near-control levels. This uptake was abolished in the presence of FCCP (10(-6)M). The results suggest that endogenous levels of DA and ATP contribute to the reserpine- and ATP-insensitive DA accumulation observed in vesicles from untreated animals. HPLC analysis demonstrated no conversion of DA to norepinephrine (NE) in the course of the experiments.
mesh_terms: D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D001921:Brain / Q000378:metabolism*; D002021:Buffers; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone / Q000494:pharmacology; D002463:Cell Membrane Permeability; D004298:Dopamine / Q000378:metabolism*; D005260:Female; D007700:Kinetics; D008297:Male; D008781:Methyltyrosines / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D012110:Reserpine / Q000494:pharmacology; D013572:Synaptic Vesicles / Q000187:drug effects / Q000378:metabolism*; D013644:Tartrates; D019805:alpha-Methyltyrosine
chemical_list: D002021:Buffers; D008781:Methyltyrosines; D013644:Tartrates; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone; D019805:alpha-Methyltyrosine; D012110:Reserpine; D000255:Adenosine Triphosphate; D004298:Dopamine; C029768:tartaric acid