Are Oxygen Radicals Implicated in the Calcium Paradox of the Rat Heart?

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No reduction in creatine kinase (CK) release during standard Ca 2+ paradox in the Langendorff perfused rat heart was afforded by anoxic perfusion, nor by addition of the radical scavengers superoxide dismutase (150,000 U/L), catalase (150,000 U/L), mannitol (15 or 50 m M), dimethylthiourea (DMTU, 10 m M), the antioxidant vitamin E (0.25 or 0.75 m M), or the iron chelator desferoxamine (0.8 m M). Even under mild Ca2+ -paradox conditions, achieved by (a) reducing the duration of the Ca2+ -free period, (b) increasing [Ca2+ ]0 during the “Ca2+ -free” period, or (c) reperfusing with 0.1 m M Ca2+, no protection was achieved by mannitol, DMTU, or desferoxamine. Perfusion with N2 did not cause a reduction in CK release caused by caffeine or dinitrophe-nol or Ca2+ paradox. We conclude that no evidence supports the hypothesis that oxygen radicals are implicated in release of CK in Ca2+ paradox

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