Immunohistochemical localization of plasminogen activator inhibitor-1 in human coronary atherosclerotic lesions involved in acute myocardial infarction.

Immunohistochemical localization of plasminogen activator inhibitor-1 (PAI-1) was studied using the streptavidin-biotin method in human atherosclerotic coronary arteries. The patients (one male and two females), whose ages ranged from 61 to 78 years, died of anteroseptal acute myocardial infarction without having received any thrombolytic therapy. PAI-1 immunoreactivities (IRs) were mainly detected in the endothelial cells, smooth muscle cells, and collagen fibers of the coronary arterial intima and not in thrombi. Remarkable immunohistochemical staining was seen in intimal collagen fibers. In one patient, intimal PAI-1 IRs partly bordered a thrombus and surrounded a large atheroma rich in cholesterol crystals. Our results suggest that PAI-1 is present in both cellular and extracellular components of human coronary atherosclerotic lesions.