We have sought evidence that arachidonic acid induces mitochondrial depolarization in isolated myocytes by a lipoxygenase (LOX) dependent mechanism, and that such depolarization could contribute to arrhythmogenesis following ischemia/reperfusion injury. A method was developed for measuring mitochondrial depolarization in isolated adult rat myocytes in suspension, using tetramethylrhodamine ethyl ester (TMRE). Addition of arachidonic acid (AA) to myocytes resulted in mitochondrial depolarization that was inhibited by the lipoxygenase inhibitor baicalein, by the reactive oxygen species (ROS) scavenger mercaptoproprionylglycine, and by the anion channel inhibitor diisothiocyanatostilbene-disulfonic acid (DIDS). AA induced mitochondrial uncoupling and mitochondrial ATPase activity in myocytes, but both were insensitive to baicalein. We conclude that the metabolic effect of AA in myocytes puts mitochondria into an energetically compromised state where membrane potential is easily changed by the DIDS-sensitive LOX/ROS-mediated opening of an inner membrane anion channel. In an in vivo anesthetized rat model of coronary artery occlusion, baicalein was found to strongly inhibit arrhythmias induced by ischemia/reperfusion injury. Arrhythmias following ischemia/reperfusion injury have previously been associated with DIDS-sensitive ROS-mediated mitochondrial depolarization, and free fatty acids including AA were previously found to accumulate during such injury. We therefore conclude that arrhythmias following ischemia/reperfusion injury could originate from mitochondrial depolarization mediated by lipoxygenase and AA.
- arachidonic acid
- mitochondrial depolarization
- Copyright © 2009, American Journal of Physiology - Heart and Circulatory Physiology