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This Article Full Text Full Text (PDF) All Versions of this Article: 286/4/H1289    most recent 00811.2003v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via ISI Web of Science (16) Citing Articles via Google Scholar Google Scholar Articles by Camara, A. K. S. Articles by Stowe, D. F. Search for Related Content PubMed PubMed Citation Articles by Camara, A. K. S. Articles by Stowe, D. F.

Hypothermia augments reactive oxygen species detected in the guinea pig isolated perfused heart

Anesthesiology Research Laboratories, Departments of ¹Anesthesiology and ²Physiology, ³Cardiovascular Research Center, The Medical College of Wisconsin, Milwaukee 53226; ⁴Research Service, Veterans Affairs Medical Center, Milwaukee 53295; ⁵Department of Biomedical Engineering, Marquette University, Milwaukee, Wisconsin 53223; and ⁶Department of Anesthesiology and Intensive Care Medicine, University Hospital Münster, 48129 Münster, Germany

Submitted 21 August 2003 ; accepted in final form 19 November 2003

Hypothermic perfusion of the heart decreases oxidative phosphorylation and increases NADH. Because O₂ and substrates remain available and respiration (electron transport system, ETS) may become impaired, we examined whether reactive oxygen species (ROS) exist in excess during hypothermic perfusion. A fiberoptic probe was placed on the left ventricular free wall of isolated guinea pig hearts to record intracellular ROS, principally superoxide (), and an extracellular reactive nitrogen reactant, principally peroxynitrite (ONOO^–), a product of nitric oxide (NO·) + . Hearts were loaded with dihydroethidium (DHE), which is oxidized by to ethidium, or were perfused with L-tyrosine, which is oxidized by ONOO^– to dityrosine (diTyr). Shifts in fluorescence were measured online; diTyr fluorescence was also measured in the coronary effluent. To validate our methods and to examine the source and identity of ROS during cold perfusion, we examined the effects of a superoxide dismutase mimetic Mn(III) tetrakis(4-benzoic acid)porphyrin chloride (MnTBAP), the nitric oxide synthase inhibitor N^G-nitro-L-arginine methyl ester (L-NAME), and several agents that impair electron flux through the ETS: menadione, sodium azide (NaN₃), and 2,3-butanedione monoxime (BDM). Drugs were given before or during cold perfusion. ROS measured by DHE was inversely proportional to the temperature between 37°C and 3°C. We found that perfusion at 17°C increased DHE threefold versus perfusion at 37°C; this was reversed by MnTBAP, but not by L-NAME or BDM, and was markedly augmented by menadione and NaN₃. Perfusion at 17°C also increased myocardial and effluent diTyr (ONOO^–) by twofold. L-NAME, MnTBAP, or BDM perfused at 37°C before cooling or during 17°C perfusion abrogated, whereas menadione and NaN₃ again enhanced the cold-induced increase in ROS. Our results suggest that hypothermia moderately enhances generation by mitochondria, whereas dismutation is markedly slowed. Also, the increase in during hypothermia reacts with available NO· to produce ONOO^–, and drug-induced dismutation eliminates the hypothermia-induced increase in .

mitochondria; complexes I, III, and IV; radical scavengers