A reversible component of cerebral injury as identified by the histochemical stain 2,3,5-triphenyltetrazolium chloride (TTC)

The extent of histochemical change following middle cerebral artery occlusion was quantitatively determined in three groups of Sprague-Dawley rats with 2,3,5-triphenyltetrazolium chloride (a marker of mitochondrial oxidative enzyme function). In group I (n=7) occlusion was maintained for 3 h, with immediate sacrifice. In group II (n=7) occlusion was maintained for 5 h, with immediate sacrifice. In group III (n=7) occlusion was maintained for 3 h, followed by a 2-h period of reperfusion prior to sacrifice. The area of injury was significantly larger (P<0.05) in the 5-h occlusion group [15±4% (mean±SD)] compared to the 3-h occlusion group (9±2%); indicating a time-dependent worsening of the histochemical detection of injury. However, the area of injury was significantly less in the reperfusion group (5±2%) compared to the group that was evaluated after 3 h of occlusion without reperfusion (9±2%); indicating that some component of the injury revealed by 2,3,5-triphenyltetrazolium chloride is potentially reversible. These data suggest that contrary to previous understanding, the histochemical abnormality revealed by 2,3,5-triphenyltetrazolium chloride is reversible in some circumstances and does not necessarily represent inevitable infarction.