@entity219 flexes its muscle: Correcting a novel analysis of XXXX for @entity219 interference uncovers a method to measure @entity219 .

@entity8862 @entity35 @entity219 @entity460 @entity18650 @entity141 @entity38461 @entity15
The divalent cation chelator @entity18650 ( @entity18650 ), often used to buffer physiological changes in cytosolic @entity141 , also binds @entity8862 with high affinity. In a recently published method (Lamboley et al. 2015. J. Gen. Physiol. http://dx.doi.org/10.1085/jgp.201411250), the absorbance shift of @entity18650 at 292 nm was successfully used to determine the total @entity460 concentrations of various skeletal muscle tissues. In the present study, we show that endogenous @entity8862 in @entity35 skeletal muscle tissue can be unknowingly measured as " @entity141 ," unless appropriate measures are taken to eliminate @entity8862 interference. We analyzed two @entity35 skeletal muscle tissues, soleus and plantaris, for total @entity460 and @entity219 using either inductively coupled plasma mass spectrometry (ICP- @entity15 ) or the @entity18650 method described above. ICP- @entity15 analysis showed that total @entity219 contents in soleus and plantaris were large enough to affect the determination of total @entity460 by the @entity18650 method ( @entity460 = 1.72    0.31 and 1.96    0.14, and @entity219 = 0.528    0.04 and 0.192    0.01; mean    standard error of the mean [SEM]; n = 5; mmole/kg, respectively). We next analyzed total @entity460 using @entity18650 but included the @entity8862 -specific chelator @entity38461 ( @entity38461 ) that buffers @entity8862 without affecting @entity141 / @entity18650 binding. We found that estimated concentrations of total @entity460 ([CaT]WM) in soleus and plantaris were reduced after @entity38461 addition ([CaT]WM = 3.71    0.62 and 3.57    0.64 without @entity38461 and 3.39    0.64 and 3.42    0.62 with @entity38461 ; mean    SEM; n = 3; mmole/kg, respectively). Thus, we show that a straightforward correction can be applied to the @entity18650 method to improve the accuracy of the determination of total @entity460 that should be applicable to most any tissue studied. In addition, we show that using @entity38461 in combination with the @entity18650 method allows one to make reasonable estimates of total @entity219 concentration that are in agreement with the direct determination of @entity219 concentration by ICP- @entity15 .
