Key result
Caffeine rapid cooling contracture induces dose-dependent sarcoplasmic reticulum swelling up to 4 mM.
Why the study?
Ultrastructural changes of the sarcoplasmic reticulum during caffeine rapid cooling contracture and tetanus in skeletal muscle were not well characterized.
Caffeine rapid cooling contracture induces swelling and potential rupture of the sarcoplasmic reticulum in frog skeletal muscle, likely associated with calcium release.
Answers are grounded in this paper and cite their sources.
Offers no clinical implications for human muscle function; leaves open translation of SR swelling mechanisms from amphibian models.
Electron microscopic studies on the ultrastructural changes of the sarcoplasmic reticulum (SR) of the skeletal muscle were performed during caffeine rapid cooling contracture (RCC). The swelling of the SR was clearly induced by RCC. The diameter of the SR fixed for the electron microscopic study at the peak tension of RCC increased with graded caffeine concentration. Mean diameters of the SR (terminal cisternae) were (29.42 +/- 9.27) X 10(-2) micron at 1 mM, (31.37 +/- 10.68) X 10(-2) micron at 2 mM, (35.33 +/- 8.60) X 10(-2) micron at 4 mM caffeine, respectively, and (20.71 +/- 6.94) X 10(-2) micron at peak tetanus. On returning to room temperature (after RCC), the enlarged SR by RCC returned to its initial state (ca. 19 X 10(-2) micron) except in the case of RCC at 4 mM caffeine concentration level. Rupture of the SR and other irreversible changes during RCC occurred at 4 mM caffeine concentration level. On the other hand, there were no remarkable alterations in ultrastructure of the SR in tetanus. No morphological changes were observed at the SR-T tubule junction (junctional gap) or in the intra-SR granules (globular particles) during RCC and tetanus. It might be suggested that the morphological changes of the SR on caffeine rapid cooling associated with Ca released from the SR.
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Yoshioka et al. (1981) studied Frog skeletal muscle. Caffeine rapid cooling contracture (RCC) vs. Tetanus / room temperature was evaluated on Mean diameters of the sarcoplasmic reticulum (terminal cisternae). Caffeine rapid cooling contracture induced swelling of the sarcoplasmic reticulum in frog skeletal muscle, with mean diameters increasing with graded caffeine concentrations up to 4 mM.
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