Detection of oxygen free radicals during ischemia in rodent heart with surface fluorometery

In cardiac myocytes, oxygen radicals are generated under conditions of reperfusion following ischemia, but whether they are generated during ischemia is controversial. We measured changes in radical formation throughout 20 min ischemia in isolated rodent (mouse) heart. A fiber optic probe was positioned facing to the left ventricle (LV) to obtain emission signal from the heart. The distance between heart and cable surface was adjusted to minimize the motion artifact. The emitted fluorescent signal was transmitted to a computer through the AD board. Hydroethidine (HE) was used as a sensitive probe. When exposed to superoxide, HE was quickly oxidized to ethidium (ET). Hearts were perfused with 100uM HE for 15–30 min followed by a 20 min global ischemia. We monitored ET formation during the experiment. We observed following the onset of ischemia a rapid increase in ET signal was seen peaking within 5 min (P<0.001). This increase was blocked by SOD mimic (MnPyP, 250μM). These data demonstrated a burst of radi...