Liu S Q, Fung Y C
Department of AMES/Bioengineering, University of California, San Diego, La Jolla 92093-0412.
J Biomech Eng. 1989 Nov;111(4):325-35. doi: 10.1115/1.3168386.
Examination of changes occurring in the zero-stress state of an organ provides a way to study cellular growth in the organ due to change of physical stresses. The zero-stress state of the aorta is not a tube. It is a sector with an opening angle that varies with the location on the aorta and changes with cellular remodeling. Blood vessel remodeling can be induced by imposing a constriction on the abdominal aorta by a metal clip (aortic banding), which causes an increase of blood pressure, hypertrophy of the aortic wall, and large change of opening angle. The correlation of the opening angle with the blood vessel wall thickness and blood pressure changes in rat's aorta due to aortic banding is presented in this report. The opening angle changes daily following the aortic banding. Blood pressure rises in vessels of the upper body, but that in the lower body decreases at first and then rises to an asymptotic value. Blood vessel wall thickness increases in rough proportion to blood pressure. Vessel diameter changes also. But the most dramatic is the course of change of the zero-stress state. Typically, the time to reach 50 percent of asymptotic hypertrophy of blood vessel wall thickness is about 3-5 days. The corresponding time for blood pressure is about 7 days. The opening angle of the zero-stress state, however, increases rapidly at first, reaches a peak in about 2 to 4 days, then decreases gradually to a reduced asymptote. The exact values of the time constants depend on the location along the aortic tree. In general, the course of change of residual strain is very different from those of the blood pressure and the blood vessel wall thickness.
对器官零应力状态下发生的变化进行检测，为研究由于物理应力变化导致的器官细胞生长提供了一种方法。主动脉的零应力状态并非是一个管状结构。它是一个扇形结构，其开口角度会随主动脉上的位置而变化，并随着细胞重塑而改变。通过用金属夹对腹主动脉施加缩窄（主动脉束带术）可诱导血管重塑，这会导致血压升高、主动脉壁肥厚以及开口角度的大幅变化。本报告展示了大鼠主动脉因主动脉束带术导致的开口角度与血管壁厚度及血压变化之间的相关性。主动脉束带术后，开口角度每天都会发生变化。上半身血管的血压升高，但下半身血管的血压起初下降，随后上升至一个渐近值。血管壁厚度大致与血压成比例增加。血管直径也会改变。但最显著的是零应力状态的变化过程。通常，血管壁厚度达到渐近肥厚的50%所需的时间约为3 - 5天。血压达到相应水平所需的时间约为7天。然而，零应力状态的开口角度起初迅速增大，在约2至4天达到峰值，然后逐渐减小至一个较低的渐近值。时间常数的确切值取决于沿主动脉树的位置。一般来说，残余应变的变化过程与血压和血管壁厚度的变化过程非常不同。
