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模拟失重大鼠肠系膜小动脉的力学特性与重塑变化及重力性对抗措施的防护效果

高放, 程九华, 白云刚, Marco Boscolo, 黄晓峰, 张向, 张立藩^*

第四军医大学 航空航天生理学教研室及教育部航空航天医学重点实验室；中心实验室，西安 710032；克兰菲尔德大学航空工程系，克兰菲尔德，MK43 0AL 英国

摘要

为进一步阐明中期模拟失重环境下，肠系膜阻力性小血管的适应性改变及重力性对抗措施的防护效果，本文对28 d模拟失重组(SUS)、对抗措施组(S + D：每日使动物恢复正常站立体位1 h，承受−Gx方向的重力作用；其余23 h仍处于模拟失重状态)，以及对照组(CON)大鼠肠系膜第三级小动脉的生物力学特性与血管壁重塑变化进行了比较。所计算的生物力学参数包括：血管在被动状态下的表观刚度(β)；血管在主动和被动状态下的周向应力(σθ)-应变(εθ)关系及其增量弹性模量(Einc,p)。血管壁胶原和弹性蛋白的数量则以其在高倍透射电镜下截面积所占的百分比定量。结果显示，SUS组的主动σθ-εθ曲线非常靠近血管的被动曲线，表明其肌源性紧张度调节功能已基本丧失；但S + D的主动曲线则非常靠近CON组，二者都远离被动曲线，明显左移，并呈抛物线状。S + D组的主动曲线反映跨壁压升高时，血管刚度主动增大使应变降低的过程；但重力性对抗措施似仍不能使其与CON组的血管完全相当。三组血管的被动生物力学特性未见有显著性差别：三组的β均值介于6.3~6.8；三组的被动σθ-εθ曲线及Einc,p随压力的变化皆呈指数型增长；上述被动态参数在三组间皆无显著性的差别。然而，三组血管胶原蛋白截面积的百分比却有显著性差别。电镜图像显示，CON与S + D组大鼠中膜平滑肌细胞间隙胶原的面积显然远大于SUS组。形态测量表明：与 CON相比，S + D与SUS组管壁中膜胶原蛋白的截面积分别减少了27%与46% (P < 0.01)；而S + D与SUS组间的差别也具有显著性意义(P < 0.05)。以上结果表明，除胶原与弹性蛋白的数量与比例因素外，血管的被动生物力学特性还取决于其它一些因素。本文从生物力学角度进一步阐明了航天飞行后立位耐力不良以及重力性对抗措施的机理。

关键词： 肌源性紧张度和反应性; 血管重塑; 飞行后心血管功能失调; 间断性人工重力

分类号：R318.01

Mechanical properties and composition of mesenteric small arteries of simulated microgravity rats with and without daily -G(x) gravitation.

Gao Fang, CHENG Jiu-Hua, BAI Yun-Gang, Marco Boscolo, HUANG Xiao-Feng, ZHANG Xiang, ZHANG Li-Fan^*

Department of Aerospace Physiology and Key Laboratory of Aerospace Medicine of Ministry of Education； Central Laboratory, School of Basic Medical Sciences, the Fourth Military Medical University, Xi’an 710032, China； Department of Aerospace Engineering, Cranfield University, Cranfield, MK 43 0AL, UK

Abstract

The aim of the present study was to evaluate the active and passive mechanical properties and wall collagen and elastin contents of mesenteric small arteries (MSAs) isolated from rats of 28-day simulated microgravity (SUS), countermeasure [S + D: SUS plus 1 h/d –Gx to simulate intermittent artificial gravity (IAG)] and control (CON) groups. Three mechanical parameters were calculated: the overall stiffness (β), circumferential stress (σθ)-strain (εθ) relationship and pressure-dependent incremental elastic modulus (Einc,p). Vessel wall collagen and elastin percentage were quantified by electron microscopy. The results demonstrate that the active mechanical behavior of MSAs differs noticeably among the three groups: the active stress-strain curve of SUS vessels is very close to the passive curve, whereas the active σθ-εθ curves of CON and S + D vessels are shifted leftward and display a parabolic shape, indicating that for MSAs isolated from S + D, but not those from SUS rats, the pressure-induced myogenic constriction can effectively stiffen the vessel wall as the CON vessels. The passive mechanical behavior of MSAs does not show significant differences among the three groups. However, the percentage of collagen is decreased in the wall of SUS and S + D compared with CON vessels in the following order: SUS < S + D < CON. Thus, the relationship between passive mechanical behavior and compositional changes may be complex and yet depends on factors other than the quantity of collagen and elastin. These findings have provided biomechanical data for the understanding of the mechanism of postflight orthostatic intolerance and its gravity-based countermeasure.

Key words: myogenic tone and reactivity; vascular remodeling; postflight cardiovascular deconditioning; intermittent artificial gravity

收稿日期：2011-10-08　　录用日期：2011-12-09

通讯作者：张立藩　　E-mail: zhanglf@fmmu.edu.cn

引用本文：

高放, 程九华, 白云刚, Marco Boscolo, 黄晓峰, 张向, 张立藩. 模拟失重大鼠肠系膜小动脉的力学特性与重塑变化及重力性对抗措施的防护效果[J]. 生理学报 2012; 64 (2): 107-120.

Gao Fang, CHENG Jiu-Hua, BAI Yun-Gang, Marco Boscolo, HUANG Xiao-Feng, ZHANG Xiang, ZHANG Li-Fan. Mechanical properties and composition of mesenteric small arteries of simulated microgravity rats with and without daily -G(x) gravitation.. Acta Physiol Sin 2012; 64 (2): 107-120 (in Chinese with English abstract).