Pipette Aspiration Measurement of Local Elastic Modulus in Aortic Walls of WHHL Rabbits. Comparison with Global Elastic Modulus Measured from Pressure-Diameter Relationship.

Abstract

Local and global mechanical properties of atherosclerotic aorta were measured in 6 Watanabe heritable hyperlipidemic (WHHL) rabbits. Descending thoracic aortas were obtained from animals aged 8 months. Local initial elastic modulus Elocal and global incremental elastic modulus Hθθ were measured with pipette aspiration technique and pressure diameter tests, respectively. Opening angles were measured as an index of residual strain. Elocal of atherosclerotic lesion (fatty streak) was 19.1±1.9 kPa (mean±SEM), which was significantly smaller than that of preserved area (38.9±7.5 kPa). Hθθ of the whole specimen was 1 260±140 kl'a at 100 mmHg, and was not statistically different from the value measured in age matched controls, Japanese White rabbits. Opening angle was significantly larger in WHHL rabbits than in their controls. These results suggest that, in the early stages of atherosclerosis. (1) the lesion is more compliant than normal aortic tissues ; (2) macroscopic mechanical properties are not sensitive to local mechanical change ; (3) residual strain increases with the development of the disease. It is important to assess local mechanical properties and residual strain when studying mechanical properties of atherosclerotic aortas.