Abstract
Ultrastructural changes of endothelial cells of cardiac microvasculature during ischemia and reperfusion were observed and compared to those of mycardial cells in isolated rat hearts, to find clues to the mechanism of reperfusion injury. The hearts were perfused for 15 minutes in the Langendorff mode and then made ischemic by occluding coronary flow on the following schedules : non-ischemic, 15, 30 and 60 minutes normothermic ischemic groups (n=5 each) . It was noted that after gloval ischemia the degree of cellular damage in myocardial cells and microvasculature became progressively worse. The most remarkable changes of the endothelial cells were loss of pinocytotic vesicles in the cytoplasm and appearance of many cytoplasmic protrusions into the lumen. The mean count of pinocytotic vesicles (per 1μm2of cytoplasm) decreased significantly to 34.2, 22.07, and 10.36 in proportion to ischemic time. As ischemia progressed, the mean value of the number of cytoplasmic protrusions into the lumen (per cell membrane 10pm long) increased significantly to 1.28, 3.00 and 6.18. In 60 min ischemia group they could not be counted because the endothelial cells were extremely damaged.
