RESUMO
Mitochondria within a cardiomyocyte form a highly dynamic network that undergoes fusion and fission events in response to acute and chronic stressors, such as hyperglycemia and diabetes mellitus. Changes in mitochondrial architecture and morphology not only reflect their capacity for oxidative phosphorylation and ATP synthesis but also impact their subcellular localization and interaction with other organelles. The role of these ultrastructural abnormalities in modulating electrophysiological properties and excitation-contraction coupling remains largely unknown and warrants direct investigation considering the growing appreciation of the functional and structural coupling between the mitochondrial network, the calcium cycling machinery, and sarcolemmal ion channels in the cardiac myocyte. In this Methods in Molecular Biology chapter, we provide a protocol that allows for a quantitative assessment of mitochondrial shape and morphology in control and diabetic hearts that had undergone detailed electrophysiological measurements using high resolution optical action potential (AP) mapping.