High-frequency sarcomeric auto-oscillations induced by heating in living neonatal cardiomyocytes of the rat
2015
Shintani, Seine A. | Oyama, Kotaro | Tamura, Ryūkihei | Ishiwata, Shin’ichi
In the present study, we investigated the effects of infra-red laser irradiation on sarcomere dynamics in living neonatal cardiomyocytes of the rat. A rapid increase in temperature to >∼38°C induced [Ca2+]i-independent high-frequency (∼5–10Hz) sarcomeric auto-oscillations (Hyperthermal Sarcomeric Oscillations; HSOs). In myocytes with the intact sarcoplasmic reticular functions, HSOs coexisted with [Ca2+]i-dependent spontaneous beating in the same sarcomeres, with markedly varying frequencies (∼10 and ∼1Hz for the former and latter, respectively). HSOs likewise occurred following blockade of the sarcoplasmic reticular functions, with the amplitude becoming larger and the frequency lower in a time-dependent manner. The present findings suggest that in the mammalian heart, sarcomeres spontaneously oscillate at higher frequencies than the sinus rhythm at temperatures slightly above the physiologically relevant levels.
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