Comparison of the properties of gamma-aminobutyric acid and L-glutamate uptake into synaptic vesicles isolated from rat brain.
Rat brain synaptic vesicles exhibit ATP-dependent uptake of gamma-[3H]amino-n-butyric acid ([3H]GABA) and L-[3H]glutamate. After hypotonic shock, the highest specific activities of uptake of both L-glutamate and GABA were recovered in the 0.4 M fraction of a sucrose gradient. The uptakes of L-glutamate and GABA were inhibited by similar, but not identical, concentrations of the mitochondrial uncoupler carbonyl cyanide m-chlorophenylhydrazone and the ionophores nigericin and gramicidin, but they were not inhibited by the K+ carrier valinomycin. N,N'-Dicyclohexyl-carbodiimide and N-ethylmaleimide, Mg2+-ATPase inhibitors, inhibited the GABA and L-glutamate uptakes similarly. Low concentrations of Cl- stimulated the vesicular uptake of L-glutamate but not that of GABA. The uptakes of both L-glutamate and GABA were inhibited by high concentrations of Cl-. These results indicate that the vesicular GABA and L-glutamate uptakes are driven by an electrochemical proton gradient generated by a similar Mg2+-ATPase. The vesicular uptake mechanisms are discussed in relation to other vesicle uptake systems.
Fykse
E M
EM
Division for Environmental Toxicology, Norwegian Defence Research Establishment, Kjeller, Norway.
Christensen
H
H
Fonnum
F
F
D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D001693:Biological Transport, Active / Q000187:drug effects; D001921:Brain / Q000648:ultrastructure*; D017301:Ca(2+) Mg(2+)-ATPase / Q000037:antagonists & inhibitors; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone / Q000494:pharmacology; D002458:Cell Fractionation; D002499:Centrifugation, Density Gradient; D002712:Chlorides / Q000494:pharmacology; D004563:Electrochemistry; D005971:Glutamates / Q000378:metabolism*; D018698:Glutamic Acid; D006096:Gramicidin / Q000494:pharmacology; D008297:Male; D009550:Nigericin / Q000494:pharmacology; D011522:Protons; D051381:Rats; D011919:Rats, Inbred Strains; D013572:Synaptic Vesicles / Q000378:metabolism*; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
D002712:Chlorides; D005971:Glutamates; D011522:Protons; D006096:Gramicidin; D018698:Glutamic Acid; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone; D005680:gamma-Aminobutyric Acid; D000255:Adenosine Triphosphate; D017301:Ca(2+) Mg(2+)-ATPase; D009550:Nigericin