Model of Ca(2+) Concentration Controlled by Sarcoplasmic Reticulum of Skeletal Muscle, Using the State Transition.

摘要

Calcium(2+) in a muscle cell is controlled by the sarcoplasmic reticulum (SR) that releases Ca(2+) through the channels, takes up Ca(2+)+ by the pumps on the SR membrane, and stores up Ca(2+) with Ca(2+) binding protein called calsequestrin (CS). This report proposed a model that represents Ca(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(2+) release channels, Ca(2+) induced Ca(2+) release channels, and Ca(2+) pumps. Estimating the amount of Ca(2+) both released and pumped up with the model, it was indicated that Ca(2+) rapidly increases from the static state as soon as nerve impulses arrive at a muscle. We further reveal that the fact that Ca(2+) pumps are located apart from Ca(2+) release channels has an important influence on generating a Ca(2+) spike signal.