Effects of blood flow and blood pressuere changes on the remodeling of arterial wall

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Chronic animal experiments have been done to know the effects of changes in blood flow and/or blood pressure on the dimensions and mechanical properties of the rat arterial wall, aiming to analyze the phenomena of functional adaptation and remodeling of vascular wall which occurs in response to stresses.1. Hypertension was induced by completely ligating the abdominal aorta (AA) between the bilateral renal arteries (RAs) for 2 days to 8 weeks. Wall stress in the circumferential direction of the left common carotid artery (LCCA) at the systolic blood pressure was maintained at a normal level for the experimental due to the increase in wall thickness, and hypertension activated smooth muscle cells.2. Blood flow in the LCCA was increased and decreased by ligating the right common carotid artery (RCCA) and the left external carotid artery, respectively, for 2 to 8 weeks. In the case of increased blood flow, the inner diameter of the LCCA increased rapidly, which served to maintain wall shear at a normal level; in the case of decreased blood flow, the diameter decreased, but the response was slower.3. Hypertension and high blood flow were simultaneously induced in the LCCA by ligating the AA between the bilateral RAs and the RCCA for 8 weeks. The wall thickness and inner of the LCCA increased so as to maintain wall circumferential stress and wall shear stress at each normal level. The activity of smooth muscle cells was increased.These results indicate that arterial wall functionally adapts itself and remodels in response to stresses, and that smooth muscle cells have an important role in this phenomenon.