Regulation of cross-bridge detachment by Ca ions at high ionic strength in molluscan catch muscle |
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Authors: | T Tameyasu |
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Institution: | (1) Department of Physiology, Teikyo University School of Medicine, 173 Tokyo, (Japan);(2) Present address: Dept of Physiology, St. Marianna University School of Medicine, Miyamae-ku, 213 Kawasaki, Japan |
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Abstract: | Summary Changes in the profile of equatorial intensities of X-ray diffraction from an intact, anterior byssal retractor muscle (ABRM) ofMytilus were examined at rest, during contracture brought about by acetylcholine (ACh) and a subsequent rigor-like contraction caused by raising the tonicity of the external solution, and after returning the tonicity to normal. The results suggest that the cross-bridges formed between thick and thin actin filaments during the ACh-contracture were maintained in the hypertonic solution and broken on decreasing the tonicity before the recovery of spacing of the actin filament lattice. A similar rigor-like contraction was induced in glycerinated ABRM by increasing salt concentration during active contraction. The rigor-like force declined rapidly when Ca++ concentration decreased. The results suggest that the detachment of the cross-bridge from the actin filament is regulated by Ca++ at high ionic strength in the ABRM. |
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Keywords: | Contraction smooth muscle Mytilus edulis |
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