Indirect Evaluation of Sarcoplasmic Reticulum Ca~(2+) Release Function in Skeletal Muscle Strips / 航天医学与医学工程

ABSTRACT

Objective To set up a simple method to measure the SR Ca2+ release function in skeletal muscle strips.Methods The time from peak tension to 75 % relaxation(TR75) during intermittent tetanic contraction(fatigue contraction) of isolated musculus soleus strips was analyzed.It was prolonged rapidly,and then shortened slowly.The ratio of maximal TR75 to initial TR75(R-TR75) indicated a balance between SR Ca2+ release and uptake.If the SR Ca2+-ATPase(SERCA) activity and inhibition extent of SERCA in fatigue contraction were identical,R-TR75 should be an index for SR Ca2+ release function.Results Higher stimulation voltage or 5 mmol/L caffeine perfusion which increased the SR Ca2+ release channel open probability induced an increase of R-TR75 from 2.5 in control to 3.0.On the contrary,inhibition of SR Ca2+ release with 5 mmol/L magnesium sulfate perfusion significantly decreased R-TR75.Inhibition of SR Ca2+ release by metabolites during fatigue contraction was recovered slowly.So R-TR75 at the second fatigued contraction was reduced after 5 or 10 min of recovery,but no significant difference after 60 min of recovery.During intermittent tetanic contraction R-TR75 was increased to be 2.9 times of normal in unloaded soleus.Conclusion The above results suggest that R-TR75 during muscle strip fatigue contraction without any change of SERCA activity can indirectly reflected SR Ca2+ release function.In 2-week unloaded soleus,the enhanced R-TR75 indicates an increase in SR Ca2+ release function.