Rigor and contracture: the role of phosphorus compounds and cytosolic Ca2+

Since in the intact myocardium the effects of ischemia lead to changes in the composition of the sarcoplasm, the sarcoplasmic factors which affect mechanical performance in ischemia cannot effectively be studied at the level of complexity found in the intact cell. Much has been learned in this respect from skinned muscle preparations, i.e. preparations where the cellular membrane is made permeable so that the ‘intracellular’ composition can be controlled by the composition of the bathing solution. These studies show that the contractile apparatus is not only sensitive to calcium, which is essential for contraction, but also to pH, inorganic phosphate, ATP, and ADP amongst others.