Abstract
PEAK tension of an excised heart muscle increases with the frequency of contraction1. This ‘staircase’ phenomenon has been attributed to changes in the distribution of Ca ions; it has been proposed that the sarcoplasmic Ca2+ concentration increases with the frequency of contraction2–4. The increase in the sarcoplasmic Ca2+ is supposed to raise the peak tension by changing the behaviour of contractile proteins; however, no such molecular change has yet been clearly demonstrated. In the present study, we have investigated the behaviour of myosin projections during the staircase phenomenon by the X-ray diffraction method, in an attempt to clarify the underlying molecular events. The results have indicated that an increase in the contraction frequency causes an increase in the number of myosin projections transferred to the vicinity of the thin filaments during contraction.
Similar content being viewed by others
Article PDF
References
Bowditch, H. P. Ber. sachs. Ges. (Akad.) Wiss. 652–689 (1871).
Langer, G. A. Circulation Res. 17, 78–89 (1965).
Orkand, R. K. J. Physiol., Lond. 196, 311–325 (1968).
Allen, D. G., Jewell, B. R. & Wood, E. H. J. Physiol., Lond. 254, 1–17 (1976).
Endoh, M. & Hashimoto, K. Jap. J. Physiol. 20, 320–331 (1970).
Blinks, J. R. J. appl. Physiol. 20, 755–757 (1965).
Huxley, H. E. & Brown, W. J. molec. Biol. 30, 384–434 (1967).
Matsubara, I., Suga, H. & Yagi, N. J. Physiol., Lond. 270, 311–320 (1977).
Matsubara, I., Kamiyama, A. & Suga, H. J. molec. Biol. 111, 121–128 (1977).
Huxley, H. E. J. molec. Biol. 37, 507–520 (1968).
Haselgrove, J. C., Stewart, M. & Huxley, H. E. Nature 261, 606–608 (1976).
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
MATSUBARA, I., YAGI, N. & ENDOH, M. Behaviour of myosin projections during the staircase phenomenon of heart muscle. Nature 273, 67 (1978). https://doi.org/10.1038/273067a0
Received:
Accepted:
Issue Date:
DOI: https://doi.org/10.1038/273067a0
This article is cited by
-
Movement of myosin heads during a heart beat
Nature (1979)
Comments
By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.