Department of Biomedical Engineering, Indiana University-Perdue University Indianapolis, Indianapolis, IN 46202, USA.
Am J Physiol Heart Circ Physiol. 2012 May 15;302(10):H2058-63. doi: 10.1152/ajpheart.00758.2011. Epub 2012 Mar 16.
The passive mechanical properties of blood vessel mainly stem from the interaction of collagen and elastin fibers, but vessel constriction is attributed to smooth muscle cell (SMC) contraction. Although the passive properties of coronary arteries have been well characterized, the active biaxial stress-strain relationship is not known. Here, we carry out biaxial (inflation and axial extension) mechanical tests in right coronary arteries that provide the active coronary stress-strain relationship in circumferential and axial directions. Based on the measurements, a biaxial active strain energy function is proposed to quantify the constitutive stress-strain relationship in the physiological range of loading. The strain energy is expressed as a Gauss error function in the physiological pressure range. In K(+)-induced vasoconstriction, the mean ± SE values of outer diameters at transmural pressure of 80 mmHg were 3.41 ± 0.17 and 3.28 ± 0.24 mm at axial stretch ratios of 1.3 and 1.5, respectively, which were significantly smaller than those in Ca(2+)-free-induced vasodilated state (i.e., 4.01 ± 0.16 and 3.75 ± 0.20 mm, respectively). The mean ± SE values of the inner and outer diameters in no-load state and the opening angles in zero-stress state were 1.69 ± 0.04 mm and 2.25 ± 0.08 mm and 126 ± 22°, respectively. The active stresses have a maximal value at the passive pressure of 80-100 mmHg and at the active pressure of 140-160 mmHg. Moreover, a mechanical analysis shows a significant reduction of mean stress and strain (averaged through the vessel wall). These findings have important implications for understanding SMC mechanics.
血管的被动力学特性主要源于胶原蛋白和弹性蛋白纤维的相互作用，但血管收缩归因于平滑肌细胞（SMC）的收缩。虽然冠状动脉的被动特性已经得到很好的描述，但主动双轴应力-应变关系尚不清楚。在这里，我们对右冠状动脉进行了双轴（充气和轴向延伸）力学测试，提供了在圆周和轴向方向上的主动冠状动脉应力-应变关系。基于这些测量结果，提出了一个双轴主动应变能函数，以量化在生理加载范围内的本构应力-应变关系。应变能在生理压力范围内表示为高斯误差函数。在 K+诱导的血管收缩中，在跨壁压力为 80mmHg 时，轴向拉伸比为 1.3 和 1.5 时的外径平均值±SE 值分别为 3.41±0.17 和 3.28±0.24mm，明显小于 Ca2+自由诱导的血管扩张状态（即 4.01±0.16 和 3.75±0.20mm）。无载状态的内、外径平均值和零应力状态的开口角分别为 1.69±0.04mm、2.25±0.08mm 和 126±22°。主动应力在被动压力为 80-100mmHg 和主动压力为 140-160mmHg 时达到最大值。此外，力学分析显示平均应力和应变（在血管壁上平均）显著降低。这些发现对理解 SMC 力学具有重要意义。
