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Force, length, and Ca(2+)-troponin C affinity in skeletal muscle
1Department of Physiology, University of Pittsburgh School of Medicine, Pennsylvania 15261.
The American Journal of Physiology
|November 1, 1991
Summary
Force generation does not affect calcium binding to troponin C in skeletal muscle. Discrepancies persist between isotopic and fluorescence methods, suggesting fluorescence probes may reflect protein interactions rather than calcium binding.
Area of Science:
- Muscle physiology
- Biochemistry
- Calcium signaling
Background:
- Previous studies show conflicting results regarding calcium binding to troponin C during force generation in skeletal muscle.
- Isotopic methods suggest no change, while fluorescence studies indicate increased binding.
Purpose of the Study:
- To re-examine the effect of force generation on Ca2+ binding to troponin C in skeletal muscle.
- To investigate discrepancies between isotopic and fluorescence measurement techniques.
Main Methods:
- Used detergent-treated rabbit psoas fibers with a modified contraction-relaxation protocol.
- Measured Ca2+ binding using a double-isotope technique during steady-state force or after relaxation induced by myosin ATPase inhibitors (vanadate, 2,3-butanedione monoxime).
- Assessed Ca2+ binding before and after reducing muscle fiber force by altering sarcomere length.
Main Results:
- No statistically significant effect of force generation or sarcomere length on Ca2+-troponin C affinity was observed.
- The discrepancy between isotopic and fluorescence methods remains unresolved.
Conclusions:
- Force generation does not appear to influence Ca2+ binding to troponin C in skeletal muscle fibers under the tested conditions.
- Fluorescence probe signals in skinned fibers might be influenced by protein-protein interactions, not solely Ca2+ binding.