Evaluation of the effect of evan's blue and triphenyltetrazolium chloride dyes on myeloperoxidase activity in canine cardiac tissue.

Myeloperoxidase (MPO) activity in postinfarction, dual-stained canine tissue in the presence of Evan's Blue (EB) and Triphenyltetrazolium chloride (TTC) was evaluated. Perfusion of EB and TTC allows quantification of the area of necrosis, area-at-risk of infarction and noninvolved, normal tissue postinfarction. EB in cardiac tissue has been reported to interfere with MPO activity used to measure polymorphonuclear leukocyte (PMN) infiltration, thus requiring that infarct size and MPO activity be measured in separate groups of animals. Admixtures of EB- or TTC-stained canine cardiac tissue extracts with MPO homogenates were found to have similar MPO activity. Addition of a constant amount of EB- or TTC-stained tissue to a standard curve of MPO activity failed to influence the concentration-activity relationship. Furthermore, EB in the presence of inflammatory cell infiltration in vivo in the mouse did not alter MPO activity. Thus, neither EB nor TTC significantly interfered with the measurement of MPO activity so that EB and/or TTC-stained tissue can be utilized to examine the role of PMN's in myocardial infarction.