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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

Received: 2011-10-08　　Accepted: 2011-12-09

Corresponding author: 张立藩　　E-mail: zhanglf@fmmu.edu.cn

Citing This Article：

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).