Dependence of the Shortening Heat on Sarcomere Length in Fibre Bundles from Frog Semitendinosus Muscles
The relation between shortening heat and sarcomere length was studied using fibre bundles dissected from frog semitendinosus muscles, as well as using whole muscles. The velocity of shortening was at its maximum. The unstimulated muscles showed a large thermoelastic absorption of heat when released at long muscle lengths. However the sarcomere length at which this thermoelasticity started to appear was longer, by at least 0.3 µm per sarcomere, in fibre bundles than in whole muscles. At the same time the amount of heat absorbed was decreased in fibre bundles. The shortening heat in fibre bundles at the sarcomere lengths ranging from 2.17 to 2.74 µm, for which no correction for the thermoelasticity was necessary, decreased linearly with sarcomere length. The shortening heat in fibre bundles at longer lengths and in whole muscles was corrected by subtracting the thermoelastic heat absorption measured separately by releasing unstimulated muscles. After the correction the shortening heat showed an almost similar dependence on sarcomere length in the range from 2.0 to 3.7 µm to that seen in fibre bundles in the sarcomere length range of 2.17 to 2.74 µm.
KeywordsFibre Bundle Muscle Length Sarcomere Length Closed Cycle Frog Skeletal Muscle
Unable to display preview. Download preview PDF.
- Gordon, A.M., Huxley, A.F. and Julian, F.J. (1968). The variation in isometric tension with sarcomere length in vertebrate muscle fibres. J. Physiol. 184: 170–192.Google Scholar
- Hill, A.V. (1953). The ‘instantaneous’ elasticity of active muscle. Proc. Roy. Soc. B. 141: 181–178.Google Scholar
- Hill, A.V. (1965). Trails and Trials in Physiology. London: Arnold.Google Scholar
- Irving, M., Homsher, E. and Lebacq, J. (1980). Dependence of the shortening heat on sarcomere length in frog skeletal muscle. Fedn. Proc. 39: 1730.Google Scholar
- Kodama, T. and Yamada, K. (1979). An explanation of the shortening heat based on the enthalpy profile of the myosin ATPase reaction. In: Cross-bridge Mechanism in Muscle Contraction, eds. Sugi, H. and Pollack, G.H., pp. 481–488. Tokyo: Univ. of Tokyo Press.Google Scholar
- Meyer, K.H. and Haselbach, C. (1949). Rubber-like properties of hair keratin. Nature 164: 3334.Google Scholar
- Ricchiuti, N.V. and Mommaerts, W.F.H.M. (1985). Technique for myothermic measurements. Physiologist Washington 8: 259.Google Scholar
- Ter Keurs, H.E.D.J., Iwazumi, T. and Pollack, G.H. (1979). The length-tension relation in skeletal muscle: revisited. In: Cross-bridge Mechanism in Muscle Contraction, eds. Sugi, H. and Pollack, G.H., pp. 277–295. Tokyo: Univ. of Tokyo Press.Google Scholar
- Yamada, K., Kometani, K. and Kobayashi, T. (1981). The relation between shortening heat and sarcomere length in frog skeletal musclel. Physiol. Soc. Japan 43: 373.Google Scholar