Intensity fluctuation spectroscopy monitors contractile activation in "resting" cardiac muscle

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Science  21 Mar 1980:
Vol. 207, Issue 4437, pp. 1369-1371
DOI: 10.1126/science.7355295


Intensity fluctuations in a laser beam scattered by nonbeating isolated rat cardiac muscle varied directly with the calcium concentrations in the bathing fluid. The steady-state level of these fluctuations varied directly with calcium-dependent force suggesting that the intensity fluctuations reflect an interaction of calcium ions with the myofilaments. The demonstration that both a portion of resting force and the frequency of intensity fluctuations vary directly with calcium even in quiescent conditions indicates that some contractile activation is present in the resting muscle.