Mitochondrial transmembrane potential changes support the concept of mitochondrial heterogeneity during apoptosis.
Dissipation of mitochondrial membrane potential (DeltaPsi(m)) and release of cytochrome c from mitochondria appear to be key events during apoptosis. The precise relationship (cause or consequence) between both is currently unclear. We previously showed in a model of serum-free cultured granulosa explants that cytochrome c is retained in a subset of respiring mitochondria until late in the apoptotic process. In this study we further investigated the issue of heterogeneity by using the DeltaPsi(m)-sensitive probe CM-H2TMRos in combination with a DNA fluorochrome. Changes of DeltaPsi(m) were assessed qualitatively by epifluorescence microscopy and were quantified using digital imaging microscopy. This approach yielded the following results: (a) CM-H2TMRos staining is a reliable and specific procedure to detect DeltaPsi(m) changes in granulosa cells explants; (b) dissipation of transmembrane potential is an early event during apoptosis preceding nuclear changes but is confined to a subpopulation of mitochondria within an individual cell; (c) in frankly apoptotic cells a few polarized mitochondria can be detected. These findings support the hypothesis that ATP needed for completion of the apoptotic cascade can be generated during apoptosis in a subset of respiring mitochondria and is not necessarily derived from anaerobic glycolysis.
Krysko
D V
DV
Department of Human Anatomy, Embryology, Histology and Medical Physics, Ghent University, Ghent, Belgium. Dmitri_Krysko@yahoo.com
Roels
F
F
Leybaert
L
L
D'Herde
K
K
D000818:Animals; D017209:Apoptosis; D002469:Cell Separation; D002478:Cells, Cultured; D003574:Cytochrome c Group / Q000378:metabolism; D005260:Female; D005456:Fluorescent Dyes; D006107:Granulosa Cells / Q000648:ultrastructure; D008564:Membrane Potentials; D008856:Microscopy, Fluorescence; D008928:Mitochondria / Q000201:enzymology / Q000502:physiology*; D011784:Quail; D013347:Subcellular Fractions / Q000648:ultrastructure; D014966:Xanthenes
D003574:Cytochrome c Group; D005456:Fluorescent Dyes; D014966:Xanthenes; C121372:mitotracker orange