HYDROGEN PEROXIDE-INDUCED OXIDATIVE STRESS TO THE MAMMALIAN HEART-MUSCLE CELL (CARDIOMYOCYTE) - NONPEROXIDATIVE PURINE AND PYRIMIDINE NUCLEOTIDE DEPLETION

Hydrogen peroxide (H2O2) overload may contribute to cardiac ischemia-r eperfusion injury. We report utilization of a previously described car diomyocyte model (J. Cell. Physiol., 149:347, 1991) to assess the effe ct of H2O2-induced oxidative stress on heart-muscle purine and pyrimid ine nucleotides and high-energy phosphates (ATP, phosphocreatine). Oxi dative stress induced by bolus H2O2 elicited the loss of cardiomyocyte purine and pyrimidine nucleotides, leading to eventual de-energizatio n upon total ATP and phosphocreatine depletion. The rate and extent of ATP and phosphocreatine loss were dependent on the degree of oxidativ e stress within the range of 50 muM to 1.0 mM H2O2. At the highest H2O 2 concentration, 5 min was sufficient to elicit appreciable cardiomyoc yte high-energy phosphate loss, the extent of which could be limited b y prompt elimination of H2O2 from the culture medium. Only H2O2 dismut ation completely prevented ATP loss during H2O2-induced oxidative stre ss, whereas various free-radical scavengers and metal chelators afford ed no significant ATP preservation. Exogenously-supplied catabolic sub strates and glycolytic or tricarboxylic acid-cycle intermediates did n ot ameliorate the observed ATP and phosphocreatine depletion, suggesti ng that cardiomyocyte de-energization during H2O2-induced oxidative st ress reflected defects in substrate utilization/energy conservation. C ompromise of cardiomyocyte nucleotide and phosphocreatine pools during H2O2-induced oxidative stress was completely dissociated from membran e peroxidative damage and maintenance of cell integrity. Cardiomyocyte de-energization in response to H2O2 overload may constitute a distinc t nonperoxidative mode of injury by which cardiomyocyte energy balance could be chronically compromised in the post-ischemic heart.