Figure 1. Mitochondrial polyP concentration is highly variable and depends on respiratory activity. (A) Original recordings of DAPI fluorescence changes in intact cardiac myocytes stimulated with 5 mM methyl-succinate followed by 5 µM FCCP from control (black) and failing myocytes (gray). DAPI fluorescence represents changes in polyP concentration. (B) Average values of maximal DAPI fluorescence after methyl-succinate (left) and minimal DAPI fluorescence during FCCP (right) addition in control (black) and heart failure (gray) cells.