Journal
AMERICAN JOURNAL OF PHYSIOLOGY-HEART AND CIRCULATORY PHYSIOLOGY
Volume 291, Issue 5, Pages H2067-H2074Publisher
AMER PHYSIOLOGICAL SOC
DOI: 10.1152/ajpheart.00272.2006
Keywords
reactive oxygen species; mitochondrial ATP; sensitive potassium channel; signaling; protein kinase C
Funding
- NHLBI NIH HHS [HL-67842, HL-36573] Funding Source: Medline
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Opening the mitochondrial ATP-sensitive K+ channel (mitoK(ATP)) increases levels of reactive oxygen species (ROS) in cardiomyocytes. This increase in ROS is necessary for cardioprotection against ischemia-reperfusion injury; however, the mechanism of mitoK(ATP)-dependent stimulation of ROS production is unknown. We examined ROS production in suspensions of isolated rat heart and liver mitochondria, using fluorescent probes that are sensitive to hydrogen peroxide. When mitochondria were treated with the K-ATP channel openers diazoxide or cromakalim, their ROS production increased by 40-50%, and this effect was blocked by 5-hydroxydecanoate. ROS production exhibited a biphasic dependence on valinomycin concentration, with peak production occurring at valinomycin concentrations that catalyze about the same K+ influx as K-ATP channel openers. ROS production decreased with higher concentrations of valinomycin and with all concentrations of a classical protonophoretic uncoupler. Our studies show that the increase in ROS is due specifically to K+ influx into the matrix and is mediated by the attendant matrix alkalinization. Myxothiazol stimulated mitoK(ATP)-dependent ROS production, whereas rotenone had no effect. This indicates that the superoxide originates in complex I ( NADH: ubiquinone oxidoreductase) of the electron transport chain.
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