Endothelial cell labeling indices in swine aortas in relation to intimal cell mass-derived atherosclerotic lesions.

In the swine abdominal aorta, most atherosclerotic lesions arise from naturally occurring collections of intimal cells called intimal cell masses. The main objective of this study was to determine if the tritiated thymidine labeling index of endothelial cells lying over intimal cell masses was greater than that of endothelial cells not over intimal cell masses. A higher endothelial cell labeling index over intimal cell masses would indicate possibly a greater turnover in the area. Such a finding would suggest possible transient but repeated breaks in the endothelial cell barrier that might contribute to the initiation of the atherosclerotic lesion in intimal cell masses. In 2 groups of mash-fed swine, 2 and 11 months old, no differences were found in labeling indices of endothelial cells lying over or not over intimal cell masses. It appears that the initiation of atherosclerosis in swine abdominal aorta is not dependent upon pre-existing altered endothelial cell kinetics as measured by tritiated thymidine labeling indices. The labeling index of cells within the intimal cell mass was significantly higher than in the media; this also is obviously not dependent upon an increased labeling index of the covering endothelial cells. Another group of swine were killed at 11 months of age after receiving a hyperlipidemic diet for 270 days. The labeling index of endothelial cells over atherosclerotic lesions was significantly higher than the labeling index of endothelial cells not over lesions in these swine, and also significantly higher than that of endothelial cells over intimal cell masses in the 11-month old mash-fed group.(ABSTRACT TRUNCATED AT 250 WORDS)