Ca (2+) -force relationship of frog skeletal muscle: a dynamic model for parameter estimation
Shames, D.M.; Baker, A.J.; Weiner, M.W.; Camacho, S.A.
American Journal of Physiology 271(6 Pt 1): C2062-C2071
1996
ISSN/ISBN: 0002-9513 PMID: 8997209 Document Number: 454971
A simple mathematical model describing the dynamic connection between Ca-2+ and force generation in intact skeletal muscle from the frog has been developed from isometric force responses to cytosolic Ca-2+ concentration ((Ca-2+)-c) transients during tetanic and twitch contractions. The main element of the model is a two-state cross-bridge cycle characterized by the fractional rate of cross-bridge attachment (f-app) and the fractional rate of cross-bridge detachment (g*). While g* is constant, f-app is time varying and regulated by both (Ca-2+)-c and force. Having only four adjustable parameters, the model is mathematically unique, thereby allowing precise parameter estimation from the dynamic Ca-2+ and force data. The model should be useful for developing insights into the relative importance for force generation and relaxation of 1) the size and shape of the Ca-2+ transient, 2) the sensitivity of the fractional rate of cross-bridge attachment to both the (Ca-2+)-c and the force responses, and 3) the fractional rate of cross-bridge detachment, which is insensitive to both Ca-2+ and force.