缺氧对大鼠骨骼肌毛细血管密度和血流量的影响

背景:组织毛细血管增多,可缩短氧从毛细血管向组织细胞弥散的距离,改善组织供氧。但组织毛细血管密度与组织的代谢水平密切相关,单纯缺氧能否引起骨骼肌毛细血管密度增加尚有争议。目的:观察不同缺氧时间大鼠骨骼肌毛细血管密度和血流供应的变化规律。设计:非随机对照实验。对动物缺氧前体质量加以选择,使各组动物的体质量在缺氧末期基本接近。地点和对象:实验地点:第三军医大学病理生理学与高原生理学教研室。清洁级纯种健康Wistar大鼠64只,雌雄各半,分为4组:对照组、缺氧5d组、缺氧15d组和缺氧30d组。干预:缺氧5d组、15d组和30d组大鼠在模拟海拔5000m的减压舱中分别连续减压缺氧5,15和30d后(23h/d),对照组大鼠在舱外饲养。用肌球蛋白ATP酶(mATPase)组织化学方法显示骨骼肌Ⅰ,Ⅱ型纤维和毛细血管并进行图像分析,测定骨骼肌纤维横断面积和毛细血管密度以及单位面积内毛细血管数与肌纤维数的比值;用放射性微球法测定骨骼肌血流量和血管阻力。主要观察指标:①各组大鼠血球压积和骨骼肌血流量、血管阻力的变化。②大鼠腓肠肌Ⅰ,Ⅱ型纤维横断面积。③各组大鼠骨骼肌毛细血管密度和单位面积内毛细血管数与肌纤维数的比值。结果:缺氧5d组大鼠与对照组相比,骨骼肌纤维横断面积即出现显著缩小犤I型分别为(2254±

Effects of hypoxia on capillary density and blood flow of skeletal muscle in rats

BACKGROUND: The increase of blood capillaries in tissues can shorten the distance of oxygen diffusion from blood capillary to tissue cells and ameliorate oxygen supplement in tissues. However, capillary density is closely related to metabolic level of tissues, so it is still controversial whether mere hypoxia can induce the increase of capillary density in skeletal muscle.OBJECTIVE: To observe the changing regulations of capillary density of skeletal muscle and blood flow in rats at different time points of hypoxia.DESIGN: A non-randomized and controlled experiment. Body mass of animals before hypoxia was selected in order to achieve similar body mass of them at the end of hypoxia.SETTING and PARTICIPANTS: The experiment was completed in the Department of Pathophysiology and Institute of High Altitude Medicine,Third Military Medical University of Chinese PLA. A total of 64 Wistar rats,half male and half female, were divided into 4 groups: control group,5-day, 15-day and 30-day hypoxia group.INTERVENTIONS: Rats in the 5-day, 15-day and 30-day hypoxia group were kept in a large hypobaric chamber with a simulated elevation of 5 000 m for 5 days, 15 days and 30 days respectively(23 hours per day). Rats in the control group were kept under normobaric condition. Myosin-ATPase (mATPase) histochemistry was used to display type Ⅰ and Ⅱ fiber of skeletal muscle and blood capillary, and imaging analysis was carried out. It was also used to assay the fiber cross-sectional area(FCSA) of skeletal muscle,capillary density(CD) and ratio of capillary number/fiber number(C/F) in a unit area. Radioactive biomicrosphere method was used to assay blood flow and vascular resistance of skeletal muscle.capillary number/fiber number(C/F) in a unit area of rats in all groups.RESULTS: FCSA of skeletal muscle was significantly decreased of rats in the 5 -day hypoxia group [typeⅠwas (2254±298), (2947±235) μm2 respectively; type Ⅱ was (1 609 + 339) , (2 391 ± 223) μm2 respectively];CD of rats in the 15-day and 30 day hypoxia group was(657 +35)/mm2and(661±50)/mm2, which were significantly higher than that in the control group[(599 ±42)/mm2], but the ratio of C/F remained unchanged significantly. There was no obvious change in blood flow supply and vascular resistance among hypoxic rats and controls.CONCLUSION: Capillary proliferation does not occur in skeletal muscle of rat exposed to hypoxia merely. However, skeletal muscle fiber atrophy caused by hypoxia induces relative increase of CD.