Effect of calcium on the energy status of rat brain synaptosomes under acidosis.
Incubation of rat brain synaptosomes at pH 6.0 in Ca2+-containing medium is associated with a decrease in the ATP content and the rate of oxygen consumption. ATP/ADP ratio decreased from 6.6 +/- 0.24 at pH 7.4 to 3.2 +/- 0.17 at pH 6.0. The content of 86Rb+ and [3H]tetraphenylphosphonium measured at pH 7.4 did not change after preincubation at pH 6.0, indicating the absence of lesion of synaptosomal plasma membranes and intrasynaptosomal mitochondria. Incubation with 1 mM EGTA in Ca2+-free medium as well as addition of 1 mM ouabain or 10 microM ruthenium red prevents the effect of acidosis. Similar results were obtained when 5 mM pyruvate was used as a mitochondrial substrate instead of glucose. It is suggested that acidosis-induced decrease in the ATP level is associated with the increase in Ca2+ concentration in the cytoplasm and its transport into mitochondria. Ouabain reverses this process due to activation of Na+/Ca2+ exchange.
Levko
A V
AV
Institute of Photobiology, Academy of Sciences of Belarus, ul. Skoriny 27, Minsk, 220072 Belarus. fed@bas07.basnet.minsk.by
Aksentsev
S L
SL
Fedorovich
S V
SV
Konev
S V
SV
D000138:Acidosis / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D001921:Brain / Q000187:drug effects / Q000378:metabolism*; D002118:Calcium / Q000494:pharmacology*; D002478:Cells, Cultured; D003470:Culture Media; D004734:Energy Metabolism / Q000187:drug effects*; D066298:In Vitro Techniques; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism; D009861:Onium Compounds / Q000378:metabolism; D009943:Organophosphorus Compounds / Q000378:metabolism; D010085:Oxidative Phosphorylation / Q000187:drug effects; D010101:Oxygen Consumption / Q000187:drug effects; D051381:Rats; D012413:Rubidium / Q000378:metabolism; D013574:Synaptosomes / Q000187:drug effects / Q000378:metabolism*
D003470:Culture Media; D009861:Onium Compounds; D009943:Organophosphorus Compounds; D000255:Adenosine Triphosphate; D012413:Rubidium; D002118:Calcium; C013289:tetraphenylphosphonium