| 17600838 |
Tretter L, Takacs K, Kover K, Adam-Vizi V: Stimulation of H (2) O (2) generation by calcium in brain mitochondria respiring on alpha-glycerophosphate. IUBMB Life. 2001 Apr;51(4):263-8.
It has been reported recently (Tretter et al., 2007b) that in isolated guinea pig brain mitochondria supported by alpha-glycerophosphate (alpha-GP) reactive oxygen species (ROS) are produced through the reverse electron transport (RET) in the respiratory chain and by alpha-glycerophosphate dehydrogenase (alpha-GPDH). We studied the effect of calcium on the generation of H (2) O (2) as measured by the Amplex Red fluorescent assay in this model. H (2) O (2) production in alpha-GP-supported mitochondria was increased significantly in the presence of 100, 250, and 500 nM Ca (2+), respectively. In addition, Ca (2+) enhanced the membrane potential, the rate of oxygen consumption, and the NAD (P) H autofluorescence in these mitochondria. Direct measurement of alpha-GPDH activity showed that Ca (2+) stimulated the enzyme by decreasing the Km for alpha-GP. In those mitochondria where RET was eliminated by the Complex I inhibitor rotenone (2 microM) or due to depolarization by ADP (1 mM), the rate of H (2) O (2) formation was smaller and the stimulation of H (2) O (2) generation by Ca (2+) was prevented partly, but the stimulatory effect of Ca (2+) was still significant. These data indicate that in alpha-GP-supported mitochondria activation of alpha-GPDH by Ca (2+) leads to an accelerated RET-mediated ROS generation as well as to a stimulated ROS production by alpha-GPDH. |
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