title: Influence of intra- and extracellular acidification on free radical formation and mitochondria membrane potential in rat brain synaptosomes.
abstract: Brain ischemia is accompanied by lowering of intra- and extracellular pH. Stroke often leads to irreversible damage of synaptic transmission by unknown mechanism. We investigated an influence of lowering of pH(i) and pH(o) on free radical formation in synaptosomes. Three models of acidosis were used: (1) pH(o) 6.0 corresponding to pH(i) decrease down to 6.04; (2) pH(o) 7.0 corresponding to the lowering of pH(i) down to 6.92: (3) 1 mM amiloride corresponding to pH(i) decrease down to 6.65. We have shown that both types of extracellular acidification, but not intracellular acidification, increase 2',7'-dichlorodihydrofluorescein diacetate fluorescence that reflects free radical formation. These three treatments induce the rise of the dihydroethidium fluorescence that reports synthesis of superoxide anion. However, the impact of amiloride on superoxide anion synthesis was less than that induced by moderate extracellular acidification. Superoxide anion synthesis at pH(o) 7.0 was almost completely eliminated by mitochondrial uncoupler carbonyl cyanide 4-(trifluoromethoxy)phenylhydrazone. Furthermore, using fluorescent dyes JC-1 and rhodamine-123, we confirmed that pH(o) lowering, but not intracellular acidification, led to depolarization of intrasynaptosomal mitochondria. We have shown that pH(o) but not pH(i) lowering led to oxidative stress in neuronal presynaptic endings that might underlie the long-term irreversible changing in synaptic transmission.
authors.affiliation: Laboratory of Biophysics and Engineering of Cell, Institute of Biophysics and Cell Engineering, Akademicheskaya St., 27, Minsk 220072, Belarus.
authors.forename: Tatyana G
authors.initials: TG
authors.lastname: Pekun
authors.forename: Valeriya V
authors.initials: VV
authors.lastname: Lemeshchenko
authors.forename: Tamara I
authors.initials: TI
authors.lastname: Lyskova
authors.forename: Tatyana V
authors.initials: TV
authors.lastname: Waseem
authors.forename: Sergei V
authors.initials: SV
authors.lastname: Fedorovich
mesh_terms: D000138:Acidosis / Q000378:metabolism; D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D001921:Brain / Q000378:metabolism*; D005110:Extracellular Space / Q000378:metabolism*; D005456:Fluorescent Dyes; D006863:Hydrogen-Ion Concentration; D042541:Intracellular Space / Q000378:metabolism*; D008297:Male; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects*; D008928:Mitochondria / Q000378:metabolism; D018384:Oxidative Stress; D051381:Rats; D017208:Rats, Wistar; D013481:Superoxides / Q000378:metabolism*; D013574:Synaptosomes / Q000378:metabolism*; D014475:Uncoupling Agents / Q000494:pharmacology; D056969:Voltage-Sensitive Dye Imaging
chemical_list: D005456:Fluorescent Dyes; D014475:Uncoupling Agents; D013481:Superoxides; D000584:Amiloride