Figure 6.

ΔΨ oscillations are independent of the changes in [Ca²⁺]_m.A and B, ΔΨ oscillations occur during reperfusion irrespective of the changes in [Ca²⁺]_m in two neighboring mitochondrial clusters in a single cell in the center of an NRVM monolayer. [Ca²⁺]_m increases most likely due to [Ca²⁺]_i increase as the cell twitches during late reperfusion and decreases after the twitching stops. C and D, in two separate cardiac myocytes in the center of an NRVM monolayer, [Ca²⁺]_m increases as the reperfused cardiac myocytes start twitching. Single mitochondrial clusters depolarize or oscillate irrespective of the changes in [Ca²⁺]_m. The membrane potential of the whole mitochondrial network of the cells collapses as they undergo contracture. E, fluorescence microscopy images of TMRM and mitoGECO signals specifying the mitochondrial clusters used in panel (D). Separate measures of emission wavelengths for (A–D) are shown in Fig. S1. F, [Ca²⁺]_i increased prior to sustained mitochondrial depolarization during reperfusion. Concurrent imaging of cytosolic GSH redox potential showed a gradual increase in GSH oxidation prior to sustained ΔΨ depolarization. The numbers on the horizontal axes show the time in minutes since the beginning of reperfusion after an hour of ischemia; in (A–D), tick marks are placed every 10 min and only the first 2 labels are shown. The dashed lines in (C, D, and F) show the time of sustained depolarization and contracture. Horizontal arrows (↔) along the time axis indicate the periods of spontaneous contractions. NRVM, neonatal rat ventricular myocyte; TMRM, tetramethylrhodamine methyl ester.