Generation of hydrogen peroxide by cerebral-cortex synaptosomes. Stimulation by ionomycin and plasma-membrane depolarization.
Guinea-pig cerebral cortex synaptosomes steadily release H2O2 into the suspending medium, at the rate of 20-30 pmol min-1 mg protein-1. A transient increase of the H2O2 release is induced by the addition of 1 mM Ca2+, which declines within 60-90 s to a rate identical or slightly higher than that before Ca2+. The extra H2O2 following Ca2+ addition varies between 40-100 pmol/mg protein and is insensitive to verapamil. The H2O2 release increases strongly (up to 250 pmol min-1 mg-1) upon depletion of the synaptosomal glutathione by treatment with 1-chloro-2,4-dinitrobenzene, a substrate for glutathione transferase. This treatment however has no effect on the Ca2+-induced H2O2 transient. In these treated synaptosomes a further increase of the output of H2O2 is rapidly induced upon addition of the Ca2+ ionophore ionomycin. This increase (about 100 pmol min-1 mg-1) lasts several minutes and requires the presence of Ca2+. A similar, though less pronounced increased H2O2 release is obtained (also in the absence of Ca2+) upon depolarization of the synaptosomal plasma membrane with KCl or with veratridine.
Zoccarato
F
F
Department of Biological Chemistry, University of Padova, Italy.
Deana
R
R
Cavallini
L
L
Alexandre
A
A
D000818:Animals; D002462:Cell Membrane / Q000187:drug effects / Q000502:physiology; D002540:Cerebral Cortex / Q000378:metabolism*; D004137:Dinitrochlorobenzene / Q000494:pharmacology; D004987:Ethers / Q000494:pharmacology; D005089:Exocytosis / Q000187:drug effects; D006168:Guinea Pigs; D006861:Hydrogen Peroxide / Q000378:metabolism*; D015759:Ionomycin; D007700:Kinetics; D008564:Membrane Potentials / Q000187:drug effects; D008928:Mitochondria / Q000378:metabolism; D008995:Monoamine Oxidase / Q000378:metabolism; D013574:Synaptosomes / Q000187:drug effects / Q000378:metabolism*
D004137:Dinitrochlorobenzene; D004987:Ethers; D015759:Ionomycin; D006861:Hydrogen Peroxide; D008995:Monoamine Oxidase