ARE OXYGEN RADICALS IMPLICATED IN THE CALCIUM PARADOX OF THE RAT-HEART

No reduction in creatine kinase (CK) release during standard Ca2+ 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 mM), dimethylthiourea (DMTU, 10 mM), the antioxidant vitamin E (0.25 or 0.75 mM), or the iron chelator desferrioxamine (0.8 mM). 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 mM Ca2+, no protection was achieved by mannitol, DMTU, or desferrioxamine. Perfusion with N-2, did not cause a reduction in CK release caused by caffeine or dinitrophenol or Ca2+ paradox. We conclude that no evidence supports the hypothesis that oxygen radicals are implicated in release of CK in Ca2+ paradox.