Cross bridge slippage in skinned frog muscle fibres.
Mechanically skinned single fibres of the semitendinosus muscles of Rana esculenta were investigated at ca. 4 degrees C. The fibres were activated by a Ca2+ jump technique, which allowed the development of a steady isometric tension within several seconds of entering a calcium rich solution at 4 degrees C. Sequences of length changes of different duration and amplitude were applied to the fibre. It could be demonstrated that the fibre behaved as a Hookean spring in the case of small amplitude length changes (up to 0.5% L0, ramp duration 0.5 ms) and that a sequence of length changes induced reversible changes in fibre state. In contrast, large stretches (greater than 1% L0) induced a muscle "give" if the stretch were not immediately preceded by a release. The data was interpreted on the basis of a strain induced detachment of cross bridges in combination with a rapid reattachment of presumably the same cross bridges in a discharged position. The rates of strain induced detachment and reattachment depended on the stretch amplitude. At amplitudes exceeding 2% L0 the rates were estimated to be at least several thousands per second.
D000205:Actomyosin / Q000502:physiology; D000818:Animals; D002118:Calcium / Q000378:metabolism; D004558:Electric Stimulation; D009119:Muscle Contraction; D009126:Muscle Relaxation; D011893:Rana esculenta
D000205:Actomyosin; D002118:Calcium