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目的确定骨骼肌收缩的舒张时程可作为判断肌质网钙离子ATP酶(SERCA)活性的功能性指标,并探讨SERCA活性对后肢去负荷大鼠萎缩比目鱼肌间断强直收缩张力下降速率的调节作用。方法采用尾部悬吊大鼠模型,游离骨骼肌肌条进行灌流,观测收缩功能的改变。结果与对照组相比,去负荷4周萎缩比目鱼肌肌条在27℃灌流条件下,间断强直收缩的舒张时程(TR75)显著缩短,强直收缩张力快速下降。相反,采用SERCA活性抑制剂环匹阿尼酸(Cyclopiazonic Acid),可延长TR75时程,并恢复强直收缩张力下降速率至对照水平。较低灌流温度(22℃)降低对照大鼠比目鱼肌SERCA活性,同时减缓强直收缩张力的下降;较高温度(35℃)则产生相反的结果。低浓度咖啡因灌流不能改变萎缩比目鱼肌强直收缩下降速率;增加灌流液Ca2+浓度和钙离子载体A23187作用下,减慢强直收缩张力下降速率。结论缩短的TR75与萎缩比目鱼肌SERCA活性增加相关联,TR75可作为表征SERCA活性的功能性指标。适度抑制SERCA活性,可能通过提高肌纤维内Ca2+浓度,减缓强直收缩张力下降速率。
Objective To determine the relaxation time of skeletal muscle contraction as a functional index to determine the activity of sarcoplasmic reticulum ATPase (SERCA), and to investigate the regulation of SERCA activity on the rate of decline of tetanic contractile tonic tension . Methods Tail suspended rat model was used to perfuse skeletal muscle strips to observe the change of systolic function. Results Compared with the control group, under the condition of 27 ℃ perfusion, the diastolic duration (TR75) of intermittent tetanic contraction was significantly shortened and the tetanic contractile tension decreased rapidly. In contrast, the SERCA inhibitor Cyclopiazonic Acid prolongs the TR75 duration and restores the rate of tetanic contractile tension decline to control levels. Lower perfusion temperature (22 ° C) decreased SERCA activity in the soleus muscles of the control rats and slowed the decline of tetanic contractile tension; the higher temperature (35 ° C) produced the opposite result. Low concentrations of caffeine perfusion can not change the reduction rate of atrophy contractile contraction intensity; increased perfusion Ca2 + concentration and calcium ionophore A23187 role, slow down the decline rate of tetanic contractile tension. Conclusion The shortened TR75 correlates with the increased SERCA activity in atrophic soleus muscle. TR75 may serve as a functional indicator of SERCA activity. Moderate inhibition of SERCA activity may reduce the rate of decline of tetanic contractility by increasing Ca2 + concentration in muscle fibers.