Rapid mitochondrial repolarization upon reperfusion after cardiac ischemia.

Abstract

The mitochondrial membrane potential (ΔΨ) drives oxidative phosphorylation and alterations contribute to cardiac pathologies, but real-time assessment of ΔΨhas not been possible. Here we describe noninvasive measurements using mitochondrial heme band babsorbances, which rapidly respond to ΔΨ. Multi-wavelength absorbance spectroscopy enabled their continuous monitoring in isolated mitochondria and the perfused heart. Calibration of heme b absorbance in isolated mitochondria revealed that reduced heme brelative to total reduced heme b (fb = b/(b + b)) exhibits a sigmoidal relationship with ΔΨ. Extrapolating this relationship to the heart enabled estimation of ΔΨas 166 ± 18 mV (n = 25, mean ± s.d.). We used this approach to assess how ΔΨchanges during ischemia-reperfusion injury, an unknown limiting the understanding of ischemia-reperfusion injury. In perfused hearts, ΔΨdeclined during ischemia and rapidly reestablished upon reperfusion, supported by oxidation of the succinate accumulated during ischemia. These findings expand our understanding of ischemia-reperfusion injury.