The present study examined the hypothesis that activation of protein kinase C (PKC) by a burst of oxygen free radicals during repeated transient anoxia results in increased activity ot endogenous antioxidant enzyme. Isolated rat myocytes were preconditioned with 2 cycles of 5 minutes of anoxia and 5 minutes of reoxygenation or with exogenous Superoxide anion ( O/} generated by reaction of 0.05 units/ml xanthine oxidase with 100 umol/L xanfhine. Myocytes m culture were subjected to 60 minutes of anoxia and 60 minutes of reoxygenation. Immediately after repetitive brief anoxia, exposure to exogenous O, or pretreatment with 4-phorbol 12-myristate 13-acetate (PMA, 100 nmoi/L), a PKC activator, PKC was rapidly translocated from the cytosol to the ceil membrane which was accompanied by increased endogenous manganese Superoxide dismutase (Mn SOD) activity, decreased LDH release, less iipid peroxidation, increased cell viability, high energy phosphate preservation, and improved cell morphology at the end of 60 minutes of reoxygenation following a longer anoxia. Administration of a O,' scavenger ( 150 units/ml SOD) or a PKC inhibitor (100 nmol/L calphostin C) during the preconditioning period effectively abolished the PKC activation, which was accompanied by the loss of endogenous Mn SOD activity and myocardial protection at the end of anoxia and reoxygenation. These results indicate that mild anoxic or oxidative stress during initial preconditioning period causes the PKC activation and the increased endogenous antioxidant enzyme activity, which causes myocardial protection against anoxic injury. This work was supported by NIH research grant HL 23597.
|Original language||English (US)|
|State||Published - Dec 1 1996|
ASJC Scopus subject areas
- Molecular Biology