Dynamics of mitochondria and mitochondrial Ca²⁺ near the plasma membrane of PC12 cells: A study by multimode microscopy

The goal of this study is to examine whether there is a difference in the regulation of Ca²⁺ between mitochondria near the cell surface and mitochondria in the cytosol. Total internal reflection fluorescence and epifluorescence microscopy were used to monitor changes in the mitochondrial Ca²⁺ ([Ca²⁺]_mt,) between the mitochondria near the plasma membrane and those in the cytosol. The results show that [Ca ²⁺]_mt near the plasma membrane increased earlier and decayed slower after high K⁺ stimulation than average mitochondria in the cytosol. In addition, the changes in [Ca²⁺]_mt in the mitochondria near the cell surface after a second stimulation were larger than those induced by the first stimulation. The results provide direct evidence to support the hypothesis that mitochondria in different subcellular localization show differential responses to the influx of extracellular Ca²⁺.