title: [Effects of +Gx stress on contractility of rat diaphragm and its mechanism].
abstract: Objective. To observe the effect of sustained +Gx exposure on contractility of rat diaphragm and explore its mechanism. Method. Forty-two male Wistar rats were randomly divided into control group (underwent +1 Gx exposure, n=21) and experiment group (underwent +15 Gx for 3 min, n=21). The tension of rat diaphragm in vivo, contents of nucleoside phosphates and lactic acid in diaphragm and ultrastructure of diaphragm were measured and observed respectively. Result. 1) Compared with pre- +Gx, low-frequency tension of diaphragm of experiment group decreased significantly (P<0.01), whereas high-frequency tension did not significantly decrease after +Gx (P>0.05). As to the control group, however, the tension of diaphragm tested at a wide range of frequencies was almost unchanged (P>0.05). 2) Compared with control group, ATP decreased (P<0.01), while ADP and lactic acid contents in diaphragm increased significantly (P<0.05 and P<0.01) after +Gx in experiment group. In addition, ratios of ADP/AMP and AMP/ATP increased significantly (P<0.01). 3) After +Gx exposure, hypoxic changes in ultrastructure of rat diaphragm occurred in experiment group, but not in control group. Conclusion. Sustained +Gx exposure could cause diaphragm muscle fatigue, which was possibly due to changes in energy metabolism and ultrastructure of rat diaphragm induced by hypoxia under +Gx stress.
authors.affiliation: Institute of Space Medico-engineering, Beijing, China.
authors.forename: Bin
authors.initials: B
authors.lastname: Wu
authors.forename: Guang-xing
authors.initials: GX
authors.lastname: You
authors.forename: Sheng-qiang
authors.initials: SQ
authors.lastname: Lu
authors.forename: Yue-ying
authors.initials: YY
authors.lastname: Xue
authors.forename: Xing-hua
authors.initials: XH
authors.lastname: Liu
mesh_terms: D000054:Acceleration; D000244:Adenosine Diphosphate / Q000378:metabolism; D000249:Adenosine Monophosphate / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D003964:Diaphragm / Q000378:metabolism / Q000502:physiology* / Q000648:ultrastructure*; D004734:Energy Metabolism / Q000502:physiology*; D018471:Hypergravity; D000860:Hypoxia; D019344:Lactic Acid / Q000378:metabolism; D008297:Male; D008854:Microscopy, Electron; D009119:Muscle Contraction / Q000502:physiology*; D018763:Muscle Fatigue / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar
chemical_list: D019344:Lactic Acid; D000249:Adenosine Monophosphate; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate