Different Permeability Pattern of the Aorta and Organ Arteries

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Abstract
There is some difference in the mechanisms of the initiation and progression of the atherosclerosis between the aorta and coronary and cerebral arteries. In this paper, morphological characteristics of the aorta and coronary and cerebral arteries, and their relationship to the permeability pattern were studied in the rats and rabbits at the ultrastructural level. In addition, the influence of renovascular hypertension and/or hypercholesteremia on these arteries were studied. 1. In the untreated control rabbits, reaction products of peroxidase were observed in the vesicles and intercellular junction of the endothelium and in the subendothelial space of the aorta and coronary artery. The ferritin particles were observed in the vesicles of the endothelium and in the subendothelial space of the aorta and coronary artery. But, in the cerebral artery, both the reaction product of peroxidase and ferritin particles were observed only in the vesicles of the endothelium, and they were not observed either in the intercellular junction or in the subendothelial space. 2. Unlike the aorta and the coronary artery, the intima of the cerebral artery showed the barrier function against the permeation of the tracers, as revealed by the presence of the tight or gap junction in the intercellular space. 3. In the rats with renovascular hypertension fed cholesterol for 12 weeks, the foam cell lesions and deposition of the fibrinoid materials were observed in the aorta and coronary artery with enhanced junctional and vesicular transport. No foam cell lesion was found in the cerebral artery, though the reaction product of peroxidase was observed in some intercellular space of the endothelium. 4. In the rabbits with renovascular hypertension fed cholesterol for 12 weeks, the foam cell lesions were freqnently observed in the aorta and coronary artery, but in the cerebral artery only small foam cell lesions were observed at the site of branching. 5. It was indicated that the hypertension might play an important role in the evolution of the cerebral atherosclerosis and the intimal cushion might be the predilective site for the development of atherosclerosis.

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