According to literature data nonspecific troponin TnC(2) binds calcium
in cardiac myocites slowly and does not influence calcium transient.
Therefore TnC(2) often was not taken into consideration in models of t
he intracellular calcium kinetics. The mathematical model of the intra
cellular Ca2+-binding system we developed includes TnC(2) as a ligand.
Rate constants accepted for the complexation of Ca2+ by intracellular
ligands give good agreement of the theoretical data with observed phy
siological ones. We compared the results of numerical experiments on t
his model with similar results obtained on the other model where TnC(2
) had been ignored. Some essential differences were revealed. In the m
odel without TnC(2) the fraction of calcium binding to specific tropon
in TnC(1) always is smaller than the fraction of Ca2+ bound to the oth
er ligands together. In our model TnC(1) fraction (it regulates the me
chanical response of muscle) is bigger that means more effective Ca2+-
binding during activation of contractile proteins. The results above s
how that within the frame of our model the constants taken for Ca2+-bi
nding ligands are more substantiate.