Effect of the hypoxanthine/xanthine oxidase system on dopamine outflow from rat striatal synaptosomes.
The effect of the oxygen radical generating system, hypoxanthine/xanthine oxidase (Hx/XOD), on the spontaneous and potassium-stimulated outflow of the neurotransmitter dopamine (DA) from rat striatal synaptosomes was studied. The efficacy of some radical scavengers was also tested. DA outflow was measured by incubation of [3H]-DA prelabeled synaptosomes (P2) in Krebs-Ringer buffer, containing either normal or depolarizing K+ concentrations. The reactions were terminated by filtration of the synaptosomes through Sartorius filters. Hx/XOD increased the spontaneous DA outflow in a dose and time dependent manner. The reduction found in synaptosomal DA content could be explained by disturbances of DA uptake or reuptake. The K+ stimulated outflow was not altered by the lower doses of Hx/XOD, whereas, when very high doses of Hx/XOD were used, the K+ stimulated DA outflow was decreased. High doses of Hx/XOD may deplete the synaptosomal DA releasable pool, leaving little DA available for extra-stimulated outflow by high concentrations of K+. The K(+)-stimulated outflow of DA is a less sensitive process against radical attack than the spontaneous release of DA. A protective action of catalase, but no effect of superoxide dismutase was demonstrated in these experiments.
Poulsen
J P
JP
Institute for Surgical Research, University of Oslo, Rikshospitalet, Norway.
Lun
A
A
Scheuch
C
C
Gruetzmann
H
H
Saugstad
O D
OD
Gross
J
J
D000818:Animals; D004298:Dopamine / Q000096:biosynthesis*; D005260:Female; D016166:Free Radical Scavengers; D008297:Male; D011188:Potassium / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D013574:Synaptosomes / Q000201:enzymology / Q000378:metabolism*; D014969:Xanthine Oxidase / Q000032:analysis / Q000378:metabolism*
D016166:Free Radical Scavengers; D014969:Xanthine Oxidase; D011188:Potassium; D004298:Dopamine