Basic Research in Cardiology

, Volume 87, Issue 4, pp 344–355 | Cite as

Decreased susceptibility to arrhythmias in hypertrophied hearts of physically trained rats

  • P. Bélichard
  • D. Pruneau
  • J. L. Salzmann
  • R. Rouet
Original Contributions

Summary

The aim of this study was to investigate the propensity to develop cardiac arrhythmias during an acute period of ischemia between normal and hypertrophied (by means of a swimming training regimen) rat hearts. We used the coronary artery ligation in vivo technique which induced the occurrence of cardiac arrhythmias in rats that was followed by the determination of the occluded zone size. This study was coupled to an in vitro study using a two-compartment tissue bath in which half of the ventricular preparation was exposed to normal conditions and the other to ischemic conditions (low pH, hypoxia, and hyperkalemia). We also measured the collagen content and the DNA/protein ratio of the hearts.

Twenty-eight male Wistar rats submitted to an eight-week swimming training (SWT) and twenty-eight cage-confined matched rats were used for the studies. SWT resulted in a 14% decrease in mean body weight and an 8% increase in absolute heart weight. We also observed a resting bradycardia in the trained animals and blood pressure remained unchanged between the two groups. Collagen content was unchanged and DNA/protein ratio was lower in the left ventricle of trained animals. During a 30-min period of coronary artery ligation, SWT rats demonstrated fewer ischemia-induced arrhythmias as compared to controls. The size of the zone affected by the vasal occlusion was lower in trained animals. Electrophysiological data recorded in the two-compartment bath showed a marked prolongation of action potential duration and refractory period in the SWT rat hearts. During the 15-min period of in vitro ischemia there was a global alteration of all electrophysiological parameters which did not differ between the two groups. Our data support the hypothesis that resting bradycardia and decrease in ischemic zone size may be involved in the arrhythmogenic protection observed in hypertrophied hearts of swimming rats after an acute ligation of the left coronary artery. Our results also indicate that cardiac hypertrophy, as defined by quantitative changes in cardiac mass or by the electrophysiological alterations that are related to its development, is not necessarily associated with an increased risk for the occurrence of arrhythmias.

Key words

Exercise hypertrophy ischemia arrhythmias fibrosis 

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References

  1. 1.
    Anderson KP (1984) Sudden death, hypertension and hypertrophy. J Cardiovasc Pharmacol 6 (Suppl 3):S 498–502Google Scholar
  2. 2.
    Anversa P, Ricci R, Olivetti G (1987) Effects of exercise on the capillary vasculature of the rat heart. Circulation 75 (suppl 1): I 12-I 18Google Scholar
  3. 3.
    Bakth S, Arena J, Lee W, Torres, Haider RB, Patel PC, Lyons MM, Regan TJ (1986) Arrhythmia susceptibility and myocardial composition in diabetes. Influence of physical training. J Clin Invest 77:382–395Google Scholar
  4. 4.
    Bélichard P, Pruneau D, Rochette L (1988) Influence of spontaneous hypertension and cardiac hypertrophy on the severity of ischemic arrhythmias in the rat. Basic Res Cardiol 83:560–566Google Scholar
  5. 5.
    Bélichard P, Pruneau D, Rouet R, Salzman JL (1991) Electrophysiological responses of hypertrophied rat myocardium to combined hypoxia, hyperkalemia and acidosis. J Cardiovasc Pharmacol 12 (Suppl 2):S 141–145Google Scholar
  6. 6.
    Bernier M, Curtis MJ, Hearse DJ (1989) Ischemia-induced and reperfusion-induced arrhythmias: importance of heart rate. Am J Physiol (Heart Circ 25) 256:H21-H31Google Scholar
  7. 7.
    Bersohn MM, Scheuer J (1978) Effect of ischemia on the performance of hearts from physically trained rats. Am J Physiol 20:H215-H218Google Scholar
  8. 8.
    Clark C, Foreman MI, Kane KA, McDonald FM, Parratt JR (1980) Coronary artery ligation in anesthetized rats as a method for the production of experimental dysrhythmias and for the determination of infarct size. J Pharmacol Methods 3:357–368Google Scholar
  9. 9.
    Corr PB, Witowski FX (1983) Potential electrophysiologic mechanisms responsible for dysrhythmias associated with reperfusion of ischemic myocardium. Circulation 68:16–24Google Scholar
  10. 10.
    Curtis MJ, Macleod BA, Walker MJA (1987) Models for the study of arrhythmias in myocardial ischemia and infarction: the use of the rat. J Mol Cell Cardiol 19:399–419Google Scholar
  11. 11.
    Gülch RW (1980) The effect of elevated chronic loading on the action potential of mammalian myocardium. J Mol Cell Cardiol 12:415–420Google Scholar
  12. 12.
    Hill BT, Whatley S (1975) A simple, rapid microassay for DNA. FEBS Letters 56:20–23Google Scholar
  13. 13.
    Kohy T, Kimura S, Myerburg RJ, Bassett AL (1988) Susceptibility of hypertrophied rat hearts to ventricular fibrillation during acute ischemia. J Mol Cell Cardiol 20:159–168Google Scholar
  14. 14.
    Lepran I, Koltai M, Siegmund W, Szekeres L (1983) Coronary artery arrhythmias and determination of the ischemic area in conscious rat. J Pharmacol Methods 9:219–230Google Scholar
  15. 15.
    Lowry OH, Rosebrough HJ, Farr AL, Randall RJ (1951) Protein measurement with the folin phenol reagent. J Biol Chem 193:265–275Google Scholar
  16. 16.
    Mattfeldt T, Mall G, Krämer KL, Zeitz R, Baust H, Mann J, Hasslacher C, Waldherr R (1985) Different stereological reaction patterns of the myocardium in hypertrophy induced by exercise and pressure overload. Acta Stereol 4:211–216Google Scholar
  17. 17.
    Merx W, Yoon MS, Han J (1977) The role of local disparity on conduction and recovery on ventricular vulnerability to fibrillation. Am Heart J 94:603–610Google Scholar
  18. 18.
    McElroy CL, Gissen SA, Fishbein MC (1978) Exercise-induced reduction in myocardial infarct size after coronary artery occlusion in the rat. Circulation 57:958–962Google Scholar
  19. 19.
    Michel JB, Lattion AL, Salzmann JL, De Lourdes M, Philippe M, Camilleri JP, Corvol P (1988) Hormonal and cardiac effects of converting enzyme inhibition in myocardial infarction. Circ Res 62:641–650Google Scholar
  20. 20.
    Morena H, Janse MJ, Fiolet JWT, Krieger WJG, Crijns H, Durrer D (1980) Comparison of the effects of regional ischemia, hypoxia, hyperkalemia and acidosis on intracellular and extracellular potentials and metabolism in isolated porcine heart. Circ Res 46:634–646Google Scholar
  21. 21.
    Morris JN, Everitt MG, Pollard R, Chave SPW, Semmence AM (1980) Vigorous exercise in leisure time: protection against coronary heart disease. Lancet 2:1207–1212Google Scholar
  22. 22.
    Penpargkul S, Repke DI, Katz AM, Scheuer J (1977) Effect of physical training on calcium transport by rat cardiac sarcoplasmic reticulum. Circ Res 40:134–138Google Scholar
  23. 23.
    Rouet RH, Adamantidis MM, Honore E, Dupuis BA (1989) In vitro abnormal repetitive responses in guinea-pig ventricular myocardium exposed to combined hypoxia, hyperkalemia, and acidosis. J Applied Cardiol 4:19–29Google Scholar
  24. 24.
    Scheuer J, Tipton CK (1977) Cardiovascular adaptations to physical training. Annu Rev Physiol 39:221–251Google Scholar
  25. 25.
    Vaughan Williams EM (1986) Ventricular hypertrophy—Physiological mechanisms. J Cardiovasc Pharmacol 8 (Suppl 3):S 12–16Google Scholar
  26. 26.
    Veenstra RD, Joyner RW, Wiedmann RT, Young ML, Tan RC (1987) Effects of hypoxia, hyperkalemia, and metabolic acidosis on canine subendocardial action potential conduction. Circ Res 60:93–101Google Scholar
  27. 27.
    Walker MJA, Curtis MJ, Hearse DJ, Campbell RWF, Janse MJ, yellon DM, Cobbe SM, Cocker SJ, Harness JB, Harron DWG, Higgins AJ, Julian DG, Lab MJ, Manning AS, Northover BJ, Parratt JR, Riemersma RA, Riva E, Russell DC, Sheridan DJ, Winslow E, Woodward B (1988) The Lambeth conventions: guidelines for the study of arrhythmias in ischemia, infarction, and reperfusion. Cardiovasc Res 22:447–455Google Scholar
  28. 28.
    Williams RS, Schaible TF, Bishop T, Morey M (1984) Effects of endurance training on cholinergic and adrenergic receptors of rat heart. J Moll Cell Cardiol 16:395–403Google Scholar
  29. 29.
    Yin FCP, Spurgeon HA, Rakusan K, Weisfeldt ML, Lakatta EG (1982) Use of tibia length to quantify cardiac hypertrophy: application in aging rat. Am J Physiol (Heart Circ Physiol 12) 243:H941-H947Google Scholar
  30. 30.
    Zak P (1973) Cell proliferation during cardiac growth. Am J Cardiol 31:211–219Google Scholar

Copyright information

© Steinkopff-Verlag 1992

Authors and Affiliations

  • P. Bélichard
    • 1
  • D. Pruneau
    • 1
  • J. L. Salzmann
    • 2
  • R. Rouet
    • 3
  1. 1.Centre de recherche des laboratoires FournierDaixFrance
  2. 2.INSERM Unité 28ParisFrance
  3. 3.Faculté des sciencesCaenFrance

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