悬吊大鼠后肢骨骼肌等长收缩功能变化的动态特征

Dynamic changes in isometric twitch of hindlimb skeletal muscles from rats tail-suspended for different period

目的 观测模拟失重 1、2和 4周大鼠比目鱼肌与趾长伸肌收缩性能的变化 ,并分析萎缩比目鱼肌收缩性能变化的可能机制。 方法 采用离体骨骼肌肌条灌流技术 ,观测比目鱼肌与趾长伸肌的等长收缩功能。 结果 悬吊 1周大鼠比目鱼肌即出现萎缩 ,悬吊 2周与 4周进一步萎缩 ,在各时间点两组的差别均具有显著性或非常显著性意义。比目鱼肌等长收缩的最大张力在悬吊第 1周仅呈降低趋势 [对照组 (1 76± 0 18) g/mm2 ,悬吊组 (1 4 6± 0 2 6 ) g/mm2 ,P >0 0 5 ],第 2周的降低具有显著性意义 [(1 2 5± 0 0 9)g/mm2 ,P <0 0 5 ],第 4周则进一步降低 [(0 90± 0 0 6 )g/mm2 ,P <0 0 1]。悬吊 1周组大鼠趾长伸肌的最大张力未改变 ,2周与 4周组的降低具有非常显著性意义(P <0 0 1)。悬吊 1、2和 4周组大鼠比目鱼肌等长收缩达到最大张力一半的时间与同步对照组相比 ,两组间的差别均无显著性意义 (P >0 0 5 ) ,但是 ,悬吊 1与 2周组达到最大张力的时间与从张力峰值到舒张 75 %的时间缩短 (P <0 0 5 ) ,悬吊 4周组则进一步缩短 (P <0 0 1)。与同步对照组相比 ,悬吊组趾长伸肌的时间参数均未发生改变 (P >0 0 5 )。 结论 由于比目鱼肌最大张力的降低与其萎缩在发生时间上不同步 ,而等长收缩的时间参数?

Objective To observe dynamic changes in isometric twitch of soleus and extensor digitorum longus(EDL) from rats tail-suspended for 1, 2, and 4 weeks. Methods The isometric twitch function of isolated soleus and EDL were examined under non-circulative perfusion condition. Results The soleus/body weight(BW) was 29.11±0.02 % in 1 week tail-suspended (SUS) rats, significantly lower than that of the control (CON) (37.73±0.02 %, P<0.05). The soleus/BW in 2 and 4 weeks SUS rats was further reduced by 16.37±0.01 and 15.63±0.01 % respectively (P<0.01). The isometric developed tension (DT) began to show trend of decrease in soleus after one week of unloading (CON: 1.76±0.18 g/mm2 vs SUS: 1.46±0.26 g/mm2, P>0.05) and significantly decreased to 1.25±0.09 g/mm2 (P<0.05) and 0.90±0.06 g/mm2 (P<0.01) after two and four weeks of unloading respectively. The isometric DT had no change in EDL after 1 week of unloading, but significantly decreased after two and four weeks of unloading (P<0.01). The time to 50 % peak tension (TP 50) during twitch contraction of soleus showed no significant change in all time periods of unloading, but the time to peak tension (TPT) was progressively shortened from 45.00±2.23 ms in CON to 30.00±2.58, 28.00±7.34 and 26.67±2.11 ms after one, two and four weeks of SUS respectively.The time from peak tension to 75 % relaxation (TR 75) of soleus was also shortened from 78.33±9.46 ms in CON to 56.67±4.21, 48.00±6.63 and 46.67±6.15 ms after one, two and four weeks of SUS respectively (P<0.05～0.01). The TP 50, TPT and TR 75of EDL were not changed in SUS as compared with CON. Conclusions The results suggested that the change of contractile- relatedregulative proteins in soleus may occur earlier in the course of unloading, and the change of contractile proteins may apppear later.