CELLULAR-DAMAGE IN THE RAT-HEART CAUSED BY THE ARTIFICIAL GENERATION OF OXYGEN RADICALS

Artificially-generated O-2 radicals have been introduced into rat Lang endorff hearts by perfusion with either menadione or H2O2 Menadione (0 .2 mM) caused the release of creatine kinase (CK), but only when previ ously activated by Ca2+-free perfusion. Release was inhibited at 28 de grees C or by perfusion under N-2. Menadione still caused severe ultra structural damage when no CK release occurred, i.e. in the presence of Ca-o(2+). Menadione can also directly inhibit the CK release mechanis m. H2O2 (0.3 mM) caused ultrastructural damage, but CK release was aga in completely dependent on Ca2+-free priming. Dimethylthiourea afforde d substantial protection, suggesting that (OH)-O-. radicals are genera ted by H2O2. It is concluded that Ca2+-free perfusion causes a tempera ture-sensitive activation of the CK release system; menadione or H2O2 generate O-2 radicals that cause the release of Ca2+ intracellularly w hich triggers myofilament damage directly and which also acts synergis tically with the activated damage system to effect CK release. The res ults confirm that myofilament damage and CK release are independent da mage pathways and that the CK release mechanism requires a dual activa tion of Ca2+ depletion plus a rise in [Ca2+](i).