Note: [*] Present address: Department of Mechanical Science and Bioengineering, Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-0043, Japan; Medical Device Innovation Center, National Cheng Kung University, Tainan 704 03, Taiwan.
Note: [****] Present address: Science & Medical Systems Business Group, Hitachi High-Technologies Corporation, Hitachinaka, Ibaraki 312-8504, Japan.
Abstract: Background:Although many studies have shown that arteries change diameter in response to chronic change in blood flow (BF), keeping wall shear stress (WSS) at physiologically normal levels, relatively little is known about the effects of flow restoration after flow reduction and also the role of vascular smooth muscle (VSM) during such a remodeling process. Objective:To elucidate the biomechanical responses of the arterial wall to the restoration of normal BF after flow reduction and compare the results with our previous results observed in response to decreased BF alone. Methods:Carotid artery BF in the Wistar rat was decreased by ligation and then restored to normal levels by release of the ligation. The effects of BF changes on the biomechanical properties of the carotid arterial wall were determined from measurements of diameters and pressures of excised artery segments. Results:During BF reduction and restoration, WSS was maintained at physiological levels by changes in the internal diameter. No significant changes in the incremental elastic modulus were found in response to changes in BF. VSM tone was significantly enhanced during the changes in BF. Conclusions:Arteries change diameters in response to BF reduction and also flow restoration to normal after flow reduction, keeping WSS at physiologically normal levels. The lack of changes in vascular elasticity suggests that there were no significant changes in major wall constituents, such as elastin and collagen. VSM may play the dominant role in observed arterial remodeling and adaptation.
