Calcium-independent activation of skinned cardiac muscle by secophalloidin |
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Authors: | Bukatina Anna E Theodore Lou J Campbell Kenneth B Sieck Gary C |
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Institution: | Departments of Anesthesiology, and Physiology and Biophysics, Mayo Foundation, Jo 4-184, 200 First Street SW, Rochester, MN 55905, USA. bukatina.anna@mayo.edu |
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Abstract: | Thin filament regulation of muscle contraction is believed to be mediated by both Ca2+ and strongly bound myosin cross-bridges. We found that secophalloidin (SPH, 5-8 mM) activates cross-bridge cycling without Ca2+ causing isometric force comparable to that induced by Ca2+. At saturated SPH], Ca2+ further increased force by 20%. SPH-induced force was reversible upon washing with a relaxing solution. However, there was more than 30% irreversible loss in subsequent Ca2+-activated force. We hypothesize that SPH activates muscle via strongly bound cross-bridges. SPH-activated contraction provides a new model for studying the role of Ca2+ and cross-bridges in muscle regulation. |
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