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J Surg Res. 2011 Jan;165(1):5-14. doi: 10.1016/j.jss.2010.09.018. Epub 2010 Oct 13.

Ischemic preconditioning decreases mitochondrial proton leak and reactive oxygen species production in the postischemic heart.

Author information

  • 1Division of Cardiothoracic Surgery, The Ohio State University Medical Center, Columbus, Ohio 43210, USA. juan.crestanello@osumc.edu

Abstract

BACKGROUND:

Proton leak (H(+) leak) dissipates mitochondrial membrane potential (mΔΨ) through the re-entry of protons into the mitochondrial matrix independent of ATP synthase. Changes in H(+) leak may affect reactive oxygen species (ROS) production. We measured H(+) leak and ROS production during ischemia-reperfusion and ischemic preconditioning (IPC) and examined how changing mitochondrial respiration affected mΔΨ and ROS production.

MATERIALS AND METHODS:

Isolated rat hearts (n = 6/group) were subjected to either control-IR or IPC. Rate pressure product (RPP) was measured. Mitochondria were isolated at end reperfusion. Respiration was measured by polarography and titrated with increasing concentrations of malonate (0.5-2 mM). mΔΨ was measured using a tetraphenylphosphonium electrode. H(+) leak is the respiratory rate required to maintain membrane potential at -150 mV in the presence of oligomycin-A. Mitochondrial complex III ROS production was measured by fluorometry using Amplex-red.

RESULTS:

IPC improved recovery of RPP at end reperfusion (63% ± 4% versus 21% ± 2% in control-IR, P < 0.05). Ischemia-reperfusion caused increased H(+) leak (94 ± 12 versus 31 ± 1 nmol O/mg protein/min in non-ischemic control, P < 0.05). IPC attenuates these increases (55 ± 9 nmol O/mg protein/min, P < 0.05 versus control-IR). IPC reduced mitochondrial ROS production compared with control-IR (31 ± 2 versus 40 ± 3 nmol/mg protein/min, P < 0.05). As mitochondrial respiration decreased, mΔΨ and mitochondrial ROS production also decreased. ROS production remained lower in IPC than in control-IR for all mΔΨ and respiration rates.

CONCLUSIONS:

Increasing H(+) leak is not associated with decreased ROS production. IPC decreases both the magnitude of H(+) leak and ROS production after ischemia-reperfusion.

Copyright © 2011 Elsevier Inc. All rights reserved.

PMID:
21035133
[PubMed - indexed for MEDLINE]
PMCID:
PMC3005326
Free PMC Article

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