+G_z负荷对大鼠膈肌收缩性能及超微结构的影响

Effect of sustained ＋G_z exposure on contractility and ultrastructure of diaphragm in rats

本实验研究旨在观察＋GZ负荷对膈肌收缩性能的影响及超微结构的变化。以33只雄性SD大鼠为实验对象。分为对照组、＋GZ组及＋GZ＝辅酶Q10药物组。对照组（12只）直接处死取膈肌试验；＋GZ组（10只）予生理盐水5ml·kg-1．d－1腹腔注射3d后，经受＋GZ负荷（头向心位、自＋4GZ开始，每上升＋1Gz持续3min，直至＋10GZ，共21min）；＋GZ＋辅酶Q10药物组（11只），予辅酶Q10mg·kg－1．d－1腹腔注射3d后，经受＋GZ负荷（同＋GZ组）。以离体膈肌条电刺激方法测定膈肌张力及耐力。结果显示：＋GZ组抗疲劳耐力显著降低；＋GZ＋药物组同＋GZ组相比，在50HZ、100HZ点上，后刺激张力显著增加。在10000－20000倍电镜观察中，膈肌线粒体在＋GZ负荷后发生缺氧性改变。证实＋GZ负荷可降低膈肌疲劳耐力，表明缺血缺氧可能是＋Gz负荷下膈肌张力减弱的原因之一；辅酶Q10可部分地提高＋GZ负荷后膈肌的疲劳耐力。

The purpose of this experimental study was to investigate the effects of sustained ＋Gzexposure on contractility and ultrastructure of diaphragm. Thirty-three male adult SD rats served assubjects. They were divided into three groups: Ⅰ. Control group (n = 12), Ⅱ. +Gz group (n = 10),andⅢ. ＋Gz coenzyme Q10 prevention group (n = 11). Rats of group Ⅱ and Ⅲ underwent sustained Gzexposure in animal centrifuge from ＋4 Gz up to 10 Gz for 21 min- Rats of group Ⅲ recieved peritonealinjectionof coenzyme Q10 (5 mg·kg-1·d-1 ) for 3 days before Gz exposure. After Gz exposure the ratswere killed. Tension of isolated diaphragmatic muscle strips induced by electric stimulation,and theirtolerance to sustained (2 min) electric stimulation were tested. It was found that,in Group Ⅱ toleranceto sustained stimulation was significantly lower than that in group Ⅰ,while in group Ⅲ,fatigue tolerancewas remarkably lower than that in group Ⅰ,but higer than that in group Ⅱ. On electronic microscopicobservation,mitochondria of diaphragmatic muscle in rats of group Ⅱ,Ⅲ revealed changes induced byhgpoxia. It is concluded that: ＋Gz exposure can lower the fatigue tolerance of diaphagmlischemic hypoxia may be one of the causes of lowering of diaphragmatic muscular tension；coenzyme Q10 to someextent,can improve fatigue tolerance following Gz exposure.