Increased aortic endothelial cell death and enhanced transendothelial macromolecular transport in streptozotocin-diabetic rats

Summary Hypertension, cigarette smoking and diabetes mellitus are well-known risk factors for atherosclerosis and coronary heart disease. Repeated endothelial cell injury and increased lipid entry have been suggested as initiating events in atherogenesis. Our previous studies have demonstrated that the frequency of endothelial cell death and associated endothelial permeability were significantly increased in the aorta of spontaneously hypertensive rats and chronic oral nicotine-treated rats. In the present investigation, we examined the hypothesis that diabetes also increases the frequency of arterial endothelial cell death and hence transendothelial macromolecular transport, which may have some implications in increasing lipid entry and thus accelerating atherogenesis. Diabetes was induced in 15 male Sprague-Dawley rats by intraperitoneal injection of 60 mg streptozotocin per kg body weight. The duration of diabetes was 6 weeks. A group of 15 age-matched rats, injected only with the buffer and maintained over the same time period, served. as the controls. In en face preparations of the thoracic aorta, IgG-containing dead endothelial cells were identified by an indirect immunoperoxidase method, and endothelial leakage to Evans blue-albumin complexes was quantified by fluorescence microscopy. Diabetic rats, compared to control rats, had significantly higher values for the frequency of endothelial cell death (0.77±0.10% vs 0.38±0.04%;p<0.005 by two-tailed, unpaired Student'st-test) and the number density of Evans blue-albumin leaky foci (4.33±0.48/mm² vs 2.99±0.38/mm²;p<0.05 by two-tailed, unpairedt-test) in the aorta. It is concluded that, similar to the situations in hypertension and nicotine consumption, the observed increase in the frequency of endothelial cell death and macromolecular permeability to large molecules in the aorta in streptozotocin-induced diabetic rats suggest that these changes may contribute to accelerated atherogenesis in diabetes.