Modeling the cyclic relationship between myoplasmic [Ca2+] and isovolumic LVP in guinea-pig intact hearts

We modified a previously developed mathematical model to interpret the cyclic relationship between myoplasmic [Ca²⁺] and left ventricular pressure (LVP) in the guinea-pig intact heart and evaluated the effects of ischemia/reperfusion (IR) injury on the model parameters. Parameters descriptive of the rate of [Ca²⁺] binding to troponin C (TnC) protein on the actin myofilament decreased following IR injury indicating a reduction in myofilament sensitivity to myoplasmic [Ca²⁺]. In addition, the model predicts diastolic contracture following IR injury by a reduced rate of myofilament cross-bridges dissociation. Changes in model parameters reflect underlying pathological changes in myocardial contractility, relaxation and cytosolic Ca²⁺ handling ability, following IR injury.