The effect of calcium on the oxidation of acetaldehyde by rat liver mitochondria. |
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Authors: | A I Cederbaum |
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Institution: | Department of Biochemistry and Pathology Mount Sinai School of Medicine of the City University of New York, New York, N.Y. 10029, USA |
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Abstract: | Isolated liver mitochondria oxidized acetaldehyde in the following order: State 4< state 3< valinomycin. Ca2+, in concentrations greater than 0.10 mM, inhibited the oxidation of acetaldehyde by isolated liver mitochondria under all conditions. Valinomycin-stimulated oxidation of acetaldehyde was more sensitive to inhibition by Ca2+ than were the state 3 or 4 rates of acetaldehyde oxidation. Acetaldehyde could support an energy-dependent uptake of Ca2+ at rates about 20 percent that found with succinate. Ruthenium red, an inhibitor of Ca2+ translocation, almost completely prevented the inhibition by Ca2+, under all conditions. The addition of externally added NAD+ or NADH provided complete relief against the inhibitions by Ca2+ of the state 4 and 3 rates of acetaldehyde oxidation. Although some relief was also observed with the valinomycin-stimulated system, significant inhibition persisted. Cations such as Zn2+, Cu2+, or Hg2+ also inhibited acetaldehyde oxidation, whereas Mg2+ and Mn2+ were without effect. These cations also blocked glutamate oxidation and presumably inhibit acetaldehyde oxidation by preventing reoxidation of NADH. The greater sensitivity of the ionophore-stimulated oxidation of acetaldehyde to inhibition by Ca2+ may reflect release of intramitochondria K+, which is known to occur in the presence of Ca2+, suggesting that acetaldehyde oxidation is influenced by the cation environment within the mitochondria. |
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