Structural and Mechanical Changes in Heart Mitochondria of Rat by AFM

摘要

Mitochondria play critical roles in both the life and death of cardiac myocytes. Various factors such as loss of ATP synthesis and increase of ATP hydrolysis, impairment in ionic homeostasis, formation of reactive oxygen species (ROS) and release of proapoptotic proteins are related to the generation of irreversible damage. It has been proposed that the release of cytochrome c is caused by a swelling of the mitochondrial matrix triggered by the apoptotic stimuli. But there is a controversy about whether or not the mitochondria indeed swell -during apoptosis. In this study, we observed the morphological and property changes in heart mitochondria which were isolated from rat myocardial infarction model using AFM. The normal mitochondria showed a homogeneous distribution with similar sizes and shapes. The surfaces of normal mitochondria looked smooth and had integrity. However, irregularities in the shapes and sizes of mitochondria were observed in those of ischemic rats. And the surfaces of ischemic mitochondria became rugged. Ultrastructural analysis of mitochondria utilizing AFM demonstrated that myocardial infarction resulted in significant increase in heart mitochondrial size, as compared with that of normal mitochondria. The force-distance curve measurements were performed to investigate the change in the adhesive force of mitochondria affected by myocardial infarction. We inferred that the changes in the adhesion force of mitochondria might be related to destruction of the highly dense mitochondrial outer membrane by swelling.