THE ROLE OF NONSPECIFIC TROPONIN IN THE I NTRACELLULAR CALCIUM KINETICS OF CARDIOMYOCYTES

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.