Localized caspase-3 activation in maturing MKs is associated with a cytosol release of Cyt-c.

A double staining between the anti–caspase-3 Ab (green) and Cyt-c Ab (red) was performed. Cells were counterstained with DAPI and examined by confocal microscopy. An overlay illustration of the labeling is shown. A MK without signs of localized caspase-3 activation (A) has a typical granular labeling with the anti–Cyt-c Ab (red). This pattern of labeling corresponds to labeling in mitochondria when double labeling is performed with an anti–Bcl-2 Ab (data not shown). In contrast, in an MK having granular labeling with the anti–caspase-3 Ab (green; B), labeling with the anti–Cyt-c (red) is weaker and more diffuse, demonstrating signs of MMP in this cell. Original magnification, × 1000.