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Mechanics of rat myocardium revisited: Investigations of ultra-thin cardiac muscles under high energy demand

  • R. W. Gülch
  • G. Ebrecht
Conference paper

Summary

Disregarding the influence of thickness on elevated strength of isolated preparations inevitably leads to erroneous tension-frequency relations, especially in the range of high frequencies. Thus, much of the confusion in interpreting the atypical negative staircase phenomenon of the rat heart is due to this. In view of the fact that the rat has become the preferred laboratory animal in cardiological research, it was imperative to reinvestigate force-frequency relations using ultra-thin preparations of the rat right ventricle (d <0.1 mm). Contrary to popular opinion, it could be demonstrated that the rat myocardium shows a positive staircase in the range of physiological heart rates. An increase in tension is still attainable even at frequencies up to 600 min−1. The interval-strength relations exhibit a minimum at frequencies of 60–120 min−1, being shifted to higher frequencies with increasing diameter, vanishing completely for thick preparations (d > 1.0 mm). At high extracellular Ca++ concentration the positive staircase even of ultra-thin muscles is flattened. However, it can be reinforced when the strength, and thus the energy expenditure, is reduced by lowering the extension. The same is true for contractions under hypoxia.

From these findings it seems probable that many investigations on isolated heart muscles of the rat, as well as other species, are objectionable when done under high energy demand, as diffusion problems will certainly limit any rise in contractility.

Keywords

Papillary Muscle Negative Inotropic Effect High Stimulation Frequency High Energy Demand Heart Preparation 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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References

  1. 1.
    Brooks WM, Haseler LJ, Clarke K, Willis RJ (1986) Relation between the phosphocreatine to ATP ratio determined by 31P nuclear magnetic resonance spectroscopy and left ventricular function in underperfused guinea-pig heart. J Mol Cell Cardiol 18: 149–155PubMedCrossRefGoogle Scholar
  2. 2.
    Buckley NM, Penefsky ZJ, Litwak RS (1972) Comparative force-frequency relationships in human and other mammalian ventricular myocardium. Pflügers Arch 332: 259–270PubMedCrossRefGoogle Scholar
  3. 3.
    DiCara LV, Miller NE (1969) Heart rate learning in noncurarized state, transfer to the curarized state, and subsequent retraining in the noncurarized state. Physiol Behavior 4: 621–624CrossRefGoogle Scholar
  4. 4.
    Forester GV, Mainwood GW (1974) Interval dependent inotropic effects in the rat myocardium and the effect of calcium. Pflügers Arch 352: 189–196PubMedCrossRefGoogle Scholar
  5. 5.
    Frezza WA, Bing OHL (1976) P02-modulated performance of cardiac muscle. Am J Physiol 231: 1620–1624PubMedGoogle Scholar
  6. 6.
    Gulch RW, Jacob R (1975) Length-tension diagram and force-velocity relations of mammalian cardiac muscle under steady-state conditions. Pflügers Arch 355: 331–346PubMedCrossRefGoogle Scholar
  7. 7.
    Gülch RW (1986) The concept of “end-systolic” pressure-volume and length-tension relations of the heart from a muscle physiologist’s point of view. Basic Res Cardiol [Suppl 1] 81: 51–57Google Scholar
  8. 8.
    Henderson AH, Brutsaert DL, Parmley WW, Sonnenblick EH (1969) Myocardial mechanics in papillary muscles of the rat and cat. Am J Physiol 217: 1273–1279PubMedGoogle Scholar
  9. 9.
    Henry PD (1975) Positive staircase effect in the rat heart. Am J Physiol 228: 360–364PubMedGoogle Scholar
  10. 10.
    Hoffman BF, Kelly JJ Jr (1959) Effect of rate and rhythm on contraction of rat papillary muscle. Am J Physiol 197: 1199–1204PubMedGoogle Scholar
  11. 11.
    Jacobus WE, Taylor GJ, Hollis DP, Nunnally RL (1977) Phosphorus nuclear magnetic resonance of perfused working rat hearts. Nature 265: 756–758PubMedCrossRefGoogle Scholar
  12. 12.
    Jacobus WE, Pores IH, Lucas SK, Weisfeldt ML, Flaherty JT (1982) Intracellular acidosis and contractility in the normal and ischemic heart as examined by 31P NMR. J Mol Cell Cardiol [Suppl 3] 14: 13–20CrossRefGoogle Scholar
  13. 13.
    Josephson IR, Sanchez-Chapula J, Brown AM (1984) Early outward current in rat single ventricular cells. Circ Res 54: 157–162PubMedCrossRefGoogle Scholar
  14. 14.
    Kissling G, Rupp H (1986) The influence of myosin isoenzyme pattern on increase in myocardial oxygen consumption induced by catecholamines. Basic Res Cardiol [Suppl 1] 81: 103–115Google Scholar
  15. 15.
    Koch-Weser J (1963) Effect of rate changes on strength and time course of contraction of papillary muscle. Am J Physiol 204: 451–457PubMedGoogle Scholar
  16. 16.
    Koch-Weser J, Blinks JR (1963) The influence of the interval between beats on myocardial contractility. Pharmacol Rev 15: 601–652PubMedGoogle Scholar
  17. 17.
    Kruta V, Stejskalovâ J (1960) Allure de la contractilité et fréquence optimale du myocarde auriculaire chez quelques mammifères. Arch Intern Physiol 68: 152–164CrossRefGoogle Scholar
  18. 18.
    McDowall RJS, Munro AF, Zayat AF (1955) Sodium and cardiac muscle. J Physiol 130: 615624Google Scholar
  19. 19.
    Meijler FL (1962) Staircase, rest contractions, and potentiation in the isolated rat heart. Am J Physiol 202: 636–640PubMedGoogle Scholar
  20. 20.
    Nilius B, Boldt W, Fechner G (1976) Auswirkungen der Hypertrophie auf das Potentiationsverhalten isolierter Ventrikelstreifen der Ratte. Acta Biol Med Germ 35: 1657–1664PubMedGoogle Scholar
  21. 21.
    Payet MD, Schanne OF, Ruiz-Ceretti E (1981) Frequency dependence of the ionic currents determining the action potential repolarization in rat ventricular muscle. J Mol Cell Cardiol 13: 207–215PubMedCrossRefGoogle Scholar
  22. 22.
    Penefsky ZJ, Buckley NM, Litwak RS (1972) Effect of temperature and calcium on force-frequency relationships in mammalian ventricular myocardium. Pflügers Arch 332: 271–282PubMedCrossRefGoogle Scholar
  23. 23.
    Roos A, Boron WF (1981) Intracellular pH. Physiol Rev 61: 296–434PubMedGoogle Scholar
  24. 24.
    Steenbergen C, Delleuw G, Rich T, Williamson JR (1977) Effects of acidosis and ischemia on contractility and intracellular pH of rat heart. Circ Res 41: 849–858PubMedCrossRefGoogle Scholar

Copyright information

© Springer-Verlag Berlin Heidelberg 1987

Authors and Affiliations

  • R. W. Gülch
    • 1
    • 2
  • G. Ebrecht
    • 1
  1. 1.Physiologisches Institut IIUniversität TübingenGermany
  2. 2.Institute of Physiology IIUniversity of TübingenTübingenGermany

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