Endothelial integrity and viability in the aorta of the normal rabbit and rat as evaluated with dye exclusion tests and interference contrast microscopy

Abstract

Cell viability in rabbit and rat aortae was evaluated by means of dye exclusion tests, which resulted in a differential staining of the aortic surface. A large proportion of the aortic surface was stained. Stained areas were related to branching-points. Unstained areas were covered with normal endothelial cells. Stained areas were covered with endothelium containing altered endothelial cells. Both structural and staining properties of the latter indicated irreversible injury or cell death. A number of phases was observed in the transformation of the endothelial cells to apparently dead, large globular structures, attached to the surface by processes. Media smooth muscle cells underlying injured endothelium were also injured, as judged from morphological examination and dye exclusion tests. Microthrombi were frequently found adhering to injured endothelial cells. The presence of injured endothelium and media in normal animals, in regions of the aorta where increased hemodynamic strain is likely to occur and which constitute predilection sites for atherosclerosis, indicates that the normal artery may be topically preconditioned for additional injury leading to atherosclerosis. Such additional injury could be provoked by experimental measures used to induce experimental atherosclerosis, and certain metabolic disturbances in man.