Frequency, amplitude, and propagation velocity of spontaneous Ca++-dependent contractile waves in intact adult rat cardiac muscle and isolated myocytes.
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Discussion
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Implication
Laboratory study reveals that extracellular calcium loading accelerates spontaneous sarcoplasmic reticulum contractile waves in rat cardiac cells, highlighting mechanisms of calcium overload.
Key Points
- To quantify the frequency, amplitude, and propagation dynamics of spontaneous calcium-dependent contractile waves in unstimulated intact rat papillary muscle and isolated cardiac myocytes.
- Examined intact bulk rat papillary muscle and isolated adult rat cardiac myocytes with intact sarcolemma under resting conditions.
- Used video analytics and laser-light scattering to measure contractile wave frequency, amplitude, and myofilament motion under varied calcium concentrations (2–15 mM at 23 °C), caffeine (0.5 mM), and temperatures.
- Spontaneous wave frequency was a fraction of 1 Hz in physiological calcium and accelerated up to several hertz during cell calcium loading.
- Increasing superfusate calcium (2–15 mM) increased oscillation frequency without altering amplitude, whereas caffeine (0.5 mM) and elevated temperature increased frequency while decreasing wave amplitude.
- Laser-light scattering fluctuations detected myofilament motion in bulk muscle under calcium loading but did not reflect divergent changes between wave frequency and amplitude.
Cite This Study
Kort et al. (1985) studied this question.