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PYRUVATE DEHYDROGENASE ACTIVATION IN RAT BRAIN CORTICAL SLICES BY ELEVATED CONCENTRATIONS OF EXTERNAL POTASSIUM IONS
Author(s) -
Kovachich G. B.,
Haugaard N.
Publication year - 1977
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1977.tb10651.x
Subject(s) - extracellular , ouabain , potassium , depolarization , calcium , sodium , enzyme , choline , biochemistry , chemistry , intracellular , enzyme assay , pyruvate dehydrogenase complex , phosphate , biophysics , biology , organic chemistry
— Cortical slices from rat brain were incubated in Krebs‐Ringer phosphate medium. Activity of the pyruvate dehydrogenase complex (PDH) was measured in homogenates of the incubated tissue. Increasing the extracellular KCI concentration from 5 to 75 mM caused a dose‐dependent increase in activity of this rate‐limiting mitochondrial enzyme. The increase in PDH activity, produced by high concentration of KCI. was associated with a decrease in the tissue content of ATP. Omission of calcium, or replacement of sodium by choline, reduced, and addition of ouabain prevented, the activation of the enzyme in the depolarized tissue. The mechanism by which extracellular potassium can affect PDH activity is unknown. However, it is most likely that the alterations in enzyme activity are related to changes in properties of cell membranes during depolarization leading to intracellular events directly affecting the enzyme complex. These could include alterations in the concentrations of adenine nucleotides or free calcium ions in the cell.