Effects of heat shock on the functional morphology of cell organelles observed by video-enhanced microscopy

In living astrocytes and MDCK cells we observed morphological phenomena during and after heat shock (HS) utilizing our new perfusable microchamber system, which monitors pH, pO2, pCO2, and temperature. By means of electronic light microscopy and confocal laser scanning microscopy, mitochondria were demonstrated to swell and to reduce their motility. The specific fluorescent probe MitoTracker Green revealed that the mitochondrial morphology changed from a rodlike into an annular shape with a central vacuole—findings which were corroborated by transmission electron microscopy. After HS (shift from 37°C to 45°C for 15 min) the mitochondrial membrane potential (ΔΨm) was depressed in most but not all mitochondria as monitored with the fluorescent probe JC-1. The dual emission images of JC-1 illustrated a heterogeneous red staining of distinct areas of single mitochondria. The shape changes as well as the drop of the membrane potential of the mitochondria indicated severe cellular stress and a direct intervention on the mitochondrial permeability transition. Anat Rec 255:458–464, 1999. © 1999 Wiley-Liss, Inc.