Related Experiment Videos
Myeloperoxidase activity as a quantitative assessment of neutrophil infiltration into ischemic myocardium
Insights
Neutrophil infiltration in ischemic heart damage can be quantified using a novel myeloperoxidase (MPO) assay. This method accurately measures neutrophil accumulation in cardiac tissue, correlating with infarct size and aiding research on leukocyte infiltration.
Area of Science:
- Cardiovascular Research
- Immunology
- Biomedical Assays
Background:
- Neutrophil infiltration exacerbates myocardial damage after ischemia and reperfusion.
- Accurate assessment of myocardial neutrophil content is crucial for understanding injury.
- Existing methods like histology and radiolabeling have significant limitations.
Purpose of the Study:
- To develop and validate a spectrophotometric assay for quantifying neutrophils in cardiac tissue.
- To measure neutrophil accumulation in ischemic myocardium using the myeloperoxidase (MPO) enzyme assay.
- To correlate MPO activity with neutrophil content and myocardial infarct size.
Main Methods:
- Developed a spectrophotometric assay measuring myeloperoxidase (MPO) activity in cardiac tissue.
- Induction of coronary artery occlusion and reperfusion in anesthetized dogs.
- Quantification of MPO activity over time during occlusion and reperfusion.
- Histologic analysis to confirm neutrophil accumulation and correlation with MPO activity.
Main Results:
- Neutrophil accumulation in ischemic myocardium showed a time-dependent, linear increase.
- MPO activity increased significantly from baseline to 90-min occlusion and further during 5-hr reperfusion.
- Histologic findings confirmed the temporal correlation of neutrophil infiltration.
- A direct correlation was observed between infarct size and myocardial MPO activity.
Conclusions:
- The MPO assay provides a simple, sensitive, and quantitative method for assessing myocardial neutrophil accumulation.
- This assay allows for the conversion of MPO activity units into tissue neutrophil content.
- The developed method is valuable for studying the relationship between leukocyte infiltration and myocardial injury.
Abstract:
The infiltration of neutrophils into ischemic myocardium exacerbates myocardial damage upon reperfusion, whereas drugs that inhibit neutrophil activity or function reduce infarct size. Consequently, it is important to accurately assess the myocardial neutrophil content. Histologic sections and radiolabeled cells have been used, but have major limitations. We have developed a method to measure the neutrophils present in cardiac tissue by utilizing a spectrophotometric assay for the neutrophil-specific myeloperoxidase enzyme (MPO) (Bradley et al., 1982a). Coronary artery occlusion and reperfusion in the anesthetized dog induces neutrophil accumulation into the ischemic heart, which shows a linear relationship with time. An increase in activity from 0.014 +/- 0.001 units (u) MPO/100 mg tissue to 0.091 +/- 0.02 u MPO/100 mg is already apparent at the end of the 90-min occlusion period. This activity increases over 5 hr reperfusion to 0.32 +/- 0.018 u MPO/100 mg tissue. Histologic analyses confirmed the temporal association of neutrophil accumulation. Moreover, there is a correlation between infarct size and tissue MPO activity. Measuring the MPO content in preparations of canine neutrophils, which is directly correlated with cell number, allows units of MPO activity to be converted into a tissue neutrophil content. This assay is simple, sensitive, and provides a quantitative index of myocardial neutrophil accumulation that can be used to study the relationship between leukocyte infiltration and myocardial injury.