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模拟失重对大鼠大脑中动脉与肠系膜小动脉肌源性紧张度的不同影响

林乐健, 暴军香, 白云刚, 张立藩, 马进^*

第四军医大学航空航天生理学教研室，西安 710032

摘要

本实验观察模拟失重对大鼠大脑中动脉和肠系膜三级小动脉血管的肌源性紧张度和缩血管反应的影响，以及每日 1 h 的–Gx 重力(矢量方向为由背向胸)对其是否具有防止作用。以3 天尾部悬吊模拟失重模型；以恢复正常站立体位模 拟–Gx 重力；采用压力型小动脉测量仪在含Ca2+ (2.5 mmol/L)或无Ca2+ 生理盐溶液中，测量不同管腔压力下血管的主动态 管径(active diameter, Da)和被动态管径(passive diameter, Dp)。肌源性紧张度由(Dp-Da)/Dp×100% 表示。大脑中动脉与肠系 膜三级小动脉对5- 羟色胺(5-hydroxytryptamine, 5-HT)和苯肾上腺素(phenylephrine, PE)的收缩反应性，在含Ca2+ 生理盐溶 液，管腔内压力为40 mmHg 条件下进行测定。结果显示：模拟失重3 天可引起大脑中动脉的肌源性紧张度以及对5-HT 的 收缩反应性增强，引起肠系膜三级小动脉的肌源性紧张度显著降低以及对PE 的缩血管反应性减弱；每日1 h 的–Gx 重力只 能防止肠系膜三级小动脉肌源性紧张度下降及血管收缩反应性减弱，而对于大脑中动脉两种反应性的增强均无影响。上述 结果表明：短期模拟失重可引起大脑中动脉与肠系膜小动脉血管的肌源性紧张度和收缩反应性发生不同方向的改变；每日 短时–Gx 重力负荷只对肠系膜小动脉功能下调有防止作用。

关键词： 微重力; 血管肌源性紧张度; 血管收缩反应性; 大鼠

分类号：R852.22

[Differential effect of simulated microgravity on myogenic tone of middle cerebral and mesenteric small arteries in rats.] [Ariticle in Chinese]

LIN Le-Jian, BAO Jun-Xiang, BAI Yun-Gang, ZHANG Li-Fan, MA Jin^*

LIN Le-Jian, BAO Jun-Xiang, BAI Yun-Gang, ZHANG Li-Fan, MA Jin

Abstract

The aim of the present study was to investigate the effect of a short-term (3-day) simulated microgravity with and without daily dorsoventral gravitation (–Gx) for 1 h on myogenic tone and vasoconstrictor responsiveness of the middle cerebral artery and mesenteric third-order small artery in rats. The tail-suspension (SUS) model was used to simulate cardiovascular deconditioning due to microgravity. Daily restoring to normal standing (STD) posture for 1 h was adopted to provide –Gx as the countermeasure. Segments of middle cerebral artery and mesenteric third-order small artery were isolated and cannulated. Vascular diameters in response to increased intraluminal pressure (from 20 mmHg to 120 mmHg, by 20 mmHg steps) of isolated arteries under no-flow conditions were recorded by a Pressure Myograph System in both physiologic salt solution (PSS) (active diameter, Da) and calcium-free PSS (passive diameter, Dp). The myogenic tone was calculated by (Dp–Da)/Dp×100%. Vasoconstrictor responsiveness of the isolated middle cerebral artery to serotonin and that of small mesenteric artery to phenylephrine were assessed in the PSS under an intraluminal pressure of 40 mmHg. The results showed that SUS induced an enhancement of the myogenic tone and vasoconstrictor responsiveness in the isolated middle cerebral artery but a depression of those in the small mesenteric artery. Daily STD for 1 h prevented the depression of myogenic tone and vasoconstrictor responsiveness in the small mesenteric artery, but did not prevent the functional enhancement in the middle cerebral artery. These data suggest that a short-term simulated microgravity may result in different alterations in the function of the cerebral artery and the resistance vessel in the hind-body. Moreover, only the decrease of function in these resistance vessels, not in the cerebral arteries, can be prevented by such a countermeasure of daily STD for 1 h.

Key words: Microgravity; myogenic tone; vasoconstrictor responsiveness; rat

收稿日期：2008-07-21　　录用日期：2008-09-16

通讯作者：马进　　E-mail: jin-ma@fmmu.edu.cn

引用本文：

林乐健, 暴军香, 白云刚, 张立藩, 马进. 模拟失重对大鼠大脑中动脉与肠系膜小动脉肌源性紧张度的不同影响[J]. 生理学报 2009; 61 (1): 27-34.

LIN Le-Jian, BAO Jun-Xiang, BAI Yun-Gang, ZHANG Li-Fan, MA Jin. [Differential effect of simulated microgravity on myogenic tone of middle cerebral and mesenteric small arteries in rats.] [Ariticle in Chinese] . Acta Physiol Sin 2009; 61 (1): 27-34 (in Chinese with English abstract).