Propidium Iodide Compares Favorably with Histology and Triphenyl Tetrazolium Chloride in the Assessment of Experimentally-induced Infarct Size

Quantitative assessment of infarct size after histology processing or by tetrazolium staining requires long reperfusion times to facilitate the delineation of the injured tissue. We evaluated the nucleic acid stain propidium iodide as an alternate technique for assessment of infarct size because it does not require extended reperfusion and is accomplished with more simple tissue processing. Eight mice underwent 45 min of coronary artery occlusion and 24 h of reperfusion, after which propidium iodide was administered and allowed to circulate for 15 min. Hearts were excised, sliced into transverse slices approximately 620 μ m thick, and photographed for determination of infarction with propidium iodide. Slices were processed by standard histology techniques, and infarction was evaluated using classical criteria of necrosis. In four other mice, infarct size was assessed by both triphenyl tetrazolium chloride and propidium iodide staining. A total of 46 slices were analysed and infarction was described as a percentage of the cross-sectional area of the slice. The correlation (r=0.94), orthogonal regression line (y=0.9 x+1.8), and the percentage of the cross-section infarcted (histology 17.5±3.0%v propidium iodide 18.5±3.0%), demonstrates that infarct size assessment after propidium iodide staining or histology processing yields the same results. Similarly, propidium iodide measurement of infarct size was comparable to that obtained with TCC staining (22.5±4.1%v 25.4±5.4%, respectively,r =0.84). We conclude that propidium iodide staining yields accurate infarct size assessment and is a simpler alternative to tetrazolium staining or histologic processing.