Evidence for a force-dependent component of calcium binding to cardiac troponin C
- Univ. of Pittsburgh School of Medicine, PA (USA)
The duration of activation in cardiac muscle is a function of the load. On the basis of studies of Ca{sup 2+} transients in muscles subjected to quick release, it has been suggested that force or shortening-mediated changes in Ca{sup 2+}-troponin C affinity may provide a mechanism for a contraction-activation feedback. This study was designed to test the hypothesis that the formation of force-generating complexes between actin and myosin enhances the affinity of cardiac troponin C for Ca{sup 2+}. This was done by first establishing the normal relationship between Ca{sup 2+} binding and force development in chemically skinned bovine ventricular muscle bundles and then comparing the Ca{sup 2+}-saturation curves obtained with relaxed and contracting muscle bundles. A double isotope technique was used to measure Ca{sup 2+} binding during ATP-induced force generation and during relaxation maintained by the phosphate analogue vanadate. The results showed that the generation of force was associated with an enhanced binding of Ca{sup 2+} to the Ca{sup 2+}-specific regulatory site of cardiac troponin C. These data provide direct evidence that feedback between force and activation in the heart may be mediated by the Ca{sup 2+}-regulatory site of troponin C.
- OSTI ID:
- 7165229
- Journal Information:
- American Journal of Physiology; (USA), Vol. 253:4; ISSN 0002-9513
- Country of Publication:
- United States
- Language:
- English
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