Calcium transients and intramembrane charge movement in skeletal muscle fibres

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Abstract
Myoplasmic Ca transients [from Rana pipiens] in response to pulse depolarizations were monitored using the dye antipyralazo III, which provides a linear measure of the change in cytoplasmic free Ca concentration. Intramembrane charge movements were recorded simultaneously with the Ca transients. Except for its initial phase, the Ca transient during each pulse closely followed the time course expected for Ca redistribution between 3 intracellular compartments with time-independent flux coefficients. The flux coefficients attained their steady values occurred just after the intramembrane charge movement was completed. This is the required sequence if charge movement were to control 1 or more coefficients for Ca fluxes across the sarcoplasmic reticular membrane.