Cooperative mechanisms of thin filament activation and their contribution to the myocardial contractile function: Assessment in a mathematical model

• Published in: Biophysics (Oxford) 2009-02, Vol.54 (1), p.39-46
• Main Authors: Katsnelson, L. B., Sulman, T. B., Solovyova, O. E., Markhasin, V. S.
• Format: Article
• Language: English
• Subjects: Biological and Medical Physics; Biophysics; Calcium; Complex Systems Biophysics; Mathematical models; Physics; Physics and Astronomy; Studies
• ISSN: 0006-3509; 1555-6654
• DOI: 10.1134/S0006350909010072

A mathematical model was used for comparative analysis of the contribution to the myocardial mechanical activity of two potentially possible variants of the cooperative influence of myosin cross-bridges on calcium activation of sarcomere actin filaments. One of these variants implies that the cooperative action of the cross-bridge on the affinity of troponin C for calcium is localized within the functional group A 7 TmTn (seven adjacent globular actin monomers, tropomyosin, and one troponin complex TnC + TnI + TnT) where this bridge is attached. The second variant is based on the assumption that cross-bridges may influence the troponin C affinity for calcium also in neighboring A 7 TmTn groups (and the closer the group is positioned relative to the bridge, the stronger is the influence on the CaTnC complex affinity in this group). The contribution of each of these two variants to the active mechanical behavior of the cardiac muscle in the contraction-relaxation cycle was assessed. It turned out that adequate simulation of the muscle mechanical activity is provided only by the second variant. Thus, the results of modeling argue in favor of the existence of just this variant of cooperativity.