Excitation-contraction coupling in skeletal muscle: Blockade by high extracellular concentrations of calcium buffers

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High concentrations (80 to 90 millimolar) of the calcium buffers EGTA and citrate (less than 10-7 molar free calcium ion) reversibly block excitation-contraction coupling in intact frog skeletal muscle fibers, but do not block caffeine-induced contractures. Solutions containing the same free calcium concentration but lower concentrations of calcium buffer (1 millimolar) do not block excitation-contraction coupling. These results suggest that excitation-contraction coupling requires the presence of calcium in a 'protected' extracellular compartment, probably the transverse tubular network, and that calcium is actively transported into this compartment from the muscle cell cytoplasm.

Original languageEnglish (US)
Pages (from-to)1270-1272
Number of pages3
Issue number4347
StatePublished - Jan 1 1978


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