Calcium Kinetics and Energetics in Myocardium Simulation Study

Abstract

We carried out a simulation study to obtain insight into the relation between calcium (Ca²⁺) transients and energy for handling Ca²⁺ in excitation-contraction (EC) coupling. The simulation incorporated basic Ca²⁺ kinetics among total released Ca²⁺ from sarcoplasmic reticulum (SR), myoplasmic free Ca²⁺ ion concentration, and troponin (Tn)-Ca complex concentration ([TnCa]). The total Ca²⁺ released from the SR was arbitrarily set as an impulse and three rate constants were used for Ca²⁺ binding to Tn, Ca²⁺ dissociation from Tn, and Ca²⁺ uptake by SR. The results showed that the peak Ca²⁺ transient varies widely as a reciprocal of the Ca²⁺ sensitivity of the contractile machinery, despite constant total released Ca²⁺ and hence, a constant energy for Ca²⁺ handling. This result suggests a disproportate relationship between the magnitude of Ca2+ transients and the energy for Ca²⁺ handling when the Ca²⁺ sensitivity of contractile machinery changes.