Mechanism of Ca/sup ++/ release from the myocyte sarcoplasmic reticulum: a model study

摘要

The mechanism of Ca/sup ++/ release from the cardiac sarcoplasmic reticulum (SR) is still uncertain. It is assumed here that the release of Ca/sup ++/ from the SR is mainly regulated by the kinetics of Ca/sup ++/ channels within the SR membrane. These kinetics are controlled, under physiological conditions, by changes in the concentration of free Ca/sup ++/ near the openings of Ca/sup ++/ channels, and are affected by Ca/sup ++/ competitors, e.g. ryanodine. The study describes this control mechanism by a combination of positive and negative control loops, associated with two types of Ca/sup ++/ binding sites located on the SR membrane: (1) activating sites with low affinity to Ca/sup ++/ and high binding rare, and (2) inactivating sites with high affinity but low binding rate. This model successfully describes the process of Ca/sup ++/ release from the SR. The ryanodine intervention supports the hypothesis of the control mechanism described by the model.