Model of Ca{sup}(2+) concentration controlled by sarcoplasmic reticulum of skeletal muscle, using the state transition

摘要

[Ca{sup}(2+)] in a muscle cell is controlled by the sarcoplasmic reticulum (SR) that releases Ca{sup}(2+) through the channels, takes up Ca{sup}(2+) by the pumps on the SR membrane, and stores up Ca{sup}(2+) with Ca{sup}(2+) binding protein called calsequestrin (CS). This report proposed a model that represents [Ca{sup}(2+)] in a muscle cell controlled by the SR using a state transition probability model in which one state means that protein in the SR is binding ligands, and the other is releasing them. The proposed model consists of 4 modules: calsequestrin, voltage dependent Ca{sup}(2+) release channels, Ca{sup}(2+) induced Ca{sup}(2+) release channels, and Ca{sup}(2+) pumps. Estimating the amount of Ca{sup}(2+) both released and pumped up with the model, it was indicated that [Ca{sup}(2+)] rapidly increases from the static state as soon as nerve impulses arrive at a muscle. We further reveal that the fact that Ca{sup}(2+) pumps are located apart from Ca{sup}(2+) release channels has an important influence on generating a Ca{sup}(2+) spike signal.