Summary
The maximum shortening velocity of the isolated, externally unloaded papillary muscle of cats, as can be obtained by quick-releases in the initial phase of isometric contractions, is clearly dependent on the Ca++-concentration of the bath solution as well as on the preload: In the range of 0.55 m-mole/1 to 4.4 m-mole/1 a doubling of the Ca++-concentration induces a mean increase of 23% in Vmax; in a range of muscle length assumed to be of physiological relevance, a rise in the extension of 10% of Lmax results in a mean augmentation of 20% in Vmax.
In order to reveal possible differences in the effect of calcium and various degrees of filament overlap, firstly, isometric mechanograms were measured under low Ca++-concentration at the muscle length of Lmax. By correspondingly lowering the muscle extension under increased Ca++-concentration the reproduction of almost the entire rising phase of these isometric mechanograms was obtained. Both these experimental conditions result in congruent force-velocity relations and consequently in identical values for Vmax. It must therefore be concluded that there exists an inner relationship between the initial time-course of the isometric force and the force-velocity relations measured during this period. The interpretation of this fact involves weighing the hypothesis of an inner frictional force dependent on velocity against that of a maximum shortening velocity dependent on the number of activated cross-bridges. The resultant consequences for the estimation of the contractile qualities of the myocardium are discussed.
The work was supported by the “Deutsche Forschungsgemeinschaft”.
Access this chapter
Tax calculation will be finalised at checkout
Purchases are for personal use only
Preview
Unable to display preview. Download preview PDF.
References
Brutsaert, D. L., V. A. Claes, M. A. Goethals: Effect of calcium on force-velocity-length relation of heart muscle of the cat. Circulat. Res. 32, 285 (1973).
Donald, T. C., K. Unnoppetchara, D. Peterson, L. L. Hefner: Effect of initial muscle length on Vmax in isotonic contraction of cardiac muscle. Amer. J. Physiol. 223, 262 (1972).
Edman, K. A. P., E. Nilsson: The mechanical parameters of myocardial contraction studied at constant length of the contractile element. Acta physiol. scand. 72, 205 (1968).
Gulch, R. W., R. Jacob: Length-tension diagram and force-velocity relations of mammalian cardiac muscle under steady-state conditions. Pflügers Arch. 355, 331 (1975).
Jacob, R., R. W. Gulch, Ch. Holubarsch: Influence of Ca-ions on the maximum velocity of shortening (Vmax) of the unloaded cat papillary muscle. Pflügers Arch. Suppl. 339, R 11 (1973).
Katz, A. M.: A Biochemist’s view point. Cardiology 57, 2 (1972).
Noble, M. I. M., T. E. Bowen, L. L. Hefner: The force-velocity relationship of cat cardiac muscle, studied by isotonic and quick-release technique. Circulat. Res. 24, 821 (1969).
Author information
Authors and Affiliations
Editor information
Editors and Affiliations
Rights and permissions
Copyright information
© 1977 Dr. Dietrich Steinkopff Verlag, Darmstadt
About this paper
Cite this paper
Gülch, R.W. (1977). The effect of preload and Ca++-ions on the time-course of the isometric force and on the force-velocity relation: Is Vmax dependent on the number of activated cross-bridges?. In: Jacob, R. (eds) The Hypertrophied Heart. Steinkopff. https://doi.org/10.1007/978-3-642-85299-2_3
Download citation
DOI: https://doi.org/10.1007/978-3-642-85299-2_3
Publisher Name: Steinkopff
Print ISBN: 978-3-7985-0482-0
Online ISBN: 978-3-642-85299-2
eBook Packages: Springer Book Archive