Effect of ischemia on heart submitochondrial superoxide production

NADH-dependent formation of superoxide anions (O2-) by rabbit cardiac submitochondrial particles (SMP) was stimulated after exposure of the isolated heart to 90 min of ischemic perfusion. This effect was more evident in the rotenone-inhibited region of the respiratory electron chain in comparison to the antimycin-inhibited region. The kinetic study of the NADH-dependent reaction showed that at the level of the rotenone-inhibited region, ischemia reduced Km value for NADH, differently from the antimycin-inhibited region where the kinetic constants remain unchanged. No significant changes of the Vmax values were observed in both SMP-producing O2- sites. The ischemic perfusions also produced a reduction of mitochondrial function, particularly evident when glutamate as substrate was studied.