Cellular Damage in the Rat Heart Caused by the Artificial Generation of Oxygen Radicals

Abstract

Artificially-generated O2 radicals have been introduced into rat Langendorff hearts by perfusion with either menadione or H2O2. Menadione (0.2 mM) caused the release of creatine kinase (CK), but only when previously activated by Ca2+-free perfusion. Release was inhibited at 28°C or by perfusion under N2. Menadione still caused severe ultrastructural damage when no CK release occurred, i.e. in the presence of Ca2+o. Menadione can also directly inhibit the CK release mechanism. H2O2 (0.3 mM) caused ultrastructural damage, but CK release was again completely dependent on Ca2+-free priming. Dimethylthiourea afforded substantial protection, suggesting that OH radicals are generated by H2O2. It is concluded that Ca2+-free perfusion causes a temperature-sensitive activation of the CK release system; menadione or H2O2 generate O2 radicals that cause the release of Ca2+ intracellularly which triggers myofilament damage directly and which also acts synergistically with the activated damage system to effect CK release. The results confirm that myofilament damage and CK release are independent damage pathways and that the CK release mechanism requires a dual activation of Ca2+ depletion plus a rise in [Ca2+]i