Stehle, Robert (2017). Force Responses and Sarcomere Dynamics of Cardiac Myofibrils Induced by Rapid Changes in [P-i]. Biophys. J., 112 (2). S. 356 - 368. CAMBRIDGE: CELL PRESS. ISSN 1542-0086
Full text not available from this repository.Abstract
The second phase of the biphasic force decay upon release of phosphate from caged phosphate was previously interpreted as a signature of kinetics of the force-generating step in the cross-bridge cycle. To test this hypothesis without using caged compounds, force responses and individual sarcomere dynamics upon rapid increases or decreases in concentration of inorganic phosphate [P-i] were investigated in calcium-activated cardiac myofibrils. Rapid increases in [P-i] induced a biphasic force decay with an initial slow decline (phase 1) and a subsequent 3-5-fold faster major decay (phase 2). Phase 2 started with the distinct elongation of a single sarcomere, the so-called sarcomere give. Give then propagated from sarcomere to sarcomere along the myofibril. Propagation speed and rate constant of phase 2 (k(+Pi(2))) had a similar [P-i]-dependence, indicating that the kinetics of the major force decay (phase 2) upon rapid increase in [P-i] is determined by sarcomere dynamics. In contrast, no give was observed during phase 1 after rapid [P-i]-increase (rate constant k(+Pi(1))) and during the single-exponential force rise (rate constant k(-pi)) after rapid [Pa-decrease. The values of k(+pi(1)) and k(-pi) were similar to the rate constant of mechanically induced force redevelopment (k(TR)) and Ca2+-induced force development (kACT) measured at same [P-i]. These results indicate that the major phase 2 of force decay upon a P-i-jump does not reflect kinetics of the force-generating step but results from sarcomere give. The other phases of P-i-induced force kinetics that occur in the absence of give yield the same information as mechanically and Ca2+-induced force kinetics (k(+Pi(1)) similar to k(-Pi) similar to k(TR) similar to k(ACT)). Model simulations indicate that P-i-induced force kinetics neither enable the separation of P-i-release from the rate-limiting transition f into force states nor differentiate whether the force generating step occurs before, along, or after the P-i-release.
| Item Type: | Journal Article | ||||||||
| Creators: |
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| URN: | urn:nbn:de:hbz:38-242266 | ||||||||
| DOI: | 10.1016/j.bpj.2016.11.005 | ||||||||
| Journal or Publication Title: | Biophys. J. | ||||||||
| Volume: | 112 | ||||||||
| Number: | 2 | ||||||||
| Page Range: | S. 356 - 368 | ||||||||
| Date: | 2017 | ||||||||
| Publisher: | CELL PRESS | ||||||||
| Place of Publication: | CAMBRIDGE | ||||||||
| ISSN: | 1542-0086 | ||||||||
| Language: | English | ||||||||
| Faculty: | Unspecified | ||||||||
| Divisions: | Unspecified | ||||||||
| Subjects: | no entry | ||||||||
| Uncontrolled Keywords: |
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| Refereed: | Yes | ||||||||
| URI: | http://kups.ub.uni-koeln.de/id/eprint/24226 |
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