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Effects of epinephrine and superoxide disumutase on cardiac myocyte function during rewarming following hypothermia
Author(s) -
Wold Ragnhild M,
Han Young Soo,
Pabelick Christina M,
Tveita Torkjel,
Prakash Y S,
Sieck Gary C
Publication year - 2007
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.21.5.a582-c
Subject(s) - hypothermia , cytosol , myocyte , reactive oxygen species , mitochondrion , superoxide dismutase , medicine , pharmacology , anesthesia , chemistry , endocrinology , oxidative stress , biochemistry , enzyme
Rewarming shock (acute cardiac failure) during resuscitation from profound hypothermia is partially ameliorated by low dose epinephrine (EPI). However, hypothermia‐induced cardiac Ca 2+ overload persists with rewarming. The reactive oxygen species (ROS) scavenger superoxide dismutase (SOD) protects isolated hearts from hypothermia‐induced Ca 2+ overload. In electrically stimulated rat cardiac myocytes loaded with Ca 2+ indicators fluo‐3 (cytosolic) and rhod‐2 (mitochondria) and imaged using confocal microscopy, we investigated the effects of EPI and SOD on cytosolic vs. mitochondrial Ca 2+ during rewarming. Myocytes were cooled from 37 to 15 °C over 1h, maintained at 15 °C for 30min, and rewarmed over 1h to 37 °C. EPI 0.125 μg/ml was administered from 27 °C upwards, and SOD 0.1 mg/ml from 15 °C upwards during rewarming. Control cells did not receive drugs. Other cells received EPI alone. Hypothermia resulted in elevated cytosolic and mitochondrial Ca 2+ . Compared to normothermia, mitochondrial Ca 2+ uptake and release was slowed by hypothermia, and not immediately reversed with rewarming. EPI prolonged mitochondrial Ca 2+ overload during rewarming. With SOD, mitochondrial as well as cytosolic Ca 2+ were comparable to controls during hypothermia and rewarming. These data suggest that during rewarming, mitochondrial Ca 2+ buffering remains impaired, and that ROS may play a role in Ca 2+ overload. Administration of EPI may exacerbate mitochondrial dysfunction, potentially worsening rewarming shock. Supported by Mayo Foundation Clinical Research grants, and NIH grants HL74309 and GM56686.