Key result
An intrinsic birefringence signal sensitive to external calcium and epinephrine was measured in mammalian cardiac muscle, reflecting sarcoplasmic reticulum activity prior to contraction.
The second component of the intrinsic birefringence signal in mammalian cardiac muscle likely reflects sarcoplasmic reticulum activity related to excitation-contraction coupling.
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Supports birefringence as a research probe of SR calcium handling in isolated myocardium; leaves open in vivo or clinical translation.
An intrinsic birefringence signal with two components occurring before sarcomere shortening was measured in mammalian cardiac muscle. The second component was sensitive to the inotropic state of the muscle as affected by external calcium concentration and epinephrine but not by changes of resting length. The second component was absent in frog heart. These results suggest that the second component of the birefringence signal reflects the activity of the sarcoplasmic reticulum related to excitation-contraction coupling processes occurring prior to onset of contraction in mammalian cardiac muscle.
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Weiss et al. (1981) studied this question. External calcium concentration and epinephrine was evaluated on Intrinsic birefringence signal components. An intrinsic birefringence signal sensitive to external calcium and epinephrine was measured in mammalian cardiac muscle, reflecting sarcoplasmic reticulum activity prior to contraction.
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