Subcellular heterogeneity of mitochondrial membrane potential: relationship with organelle distribution and intercellular contacts in normal, hypoxicand apoptotic cells

The subcellular heterogeneity of mitochondrial membrane potential (m Delta psi) was investigated in confluent and sub-confluent cultures of four cell types (human astrocytes, HEp-2, MDCK and Vero cells) in normal growth condi tions, hypoxia and apoptosis, The distribution of high-polarized mitochondr ia, detected by the potential-sensitive probe JC-1, was found to depend on: (1) the proximity to the cell edge; (2) the local absence of cell-cell con tacts; and (3) the local absence of acidic vesicles. Both hypoxia and apopt osis produced a general m Delta psi increase with different redistributions of high-polarized mitochondria, Hypoxic cells maintained high-polarized mi tochondria for over 24 hours, until cells underwent necrosis, On the other hand, apoptotic cells showed an unexpected convergence of high-polarized mi tochondria into an extremely packed mass at one side of the nucleus, in a s tage preceding nuclear condensation, but correlated to the retraction of ce ll-cell contacts.