Characterization of Cardiac Sarcoplasmic Reticulum: Dysfunction during primary myocardial ischemia: A potential source for intracellular calcium overload

  • Michael L. Hess
  • Stephen M. Krause
Part of the Developments in Cardiovascular Medicine book series (DICM, volume 39)


Breakdown of the excitation-contraction coupling system has been proposed to play a pivotal role in myocardial dysfunction during the course of acute ischemia. We tested this hypothesis by characterizing the function of the sarcoplasmic reticulum (SR) at pH 7.1 and 6.4 after 7.5, 15 and 30 minutes of canine normothermic global ischemia. At pH 7.1, isolated SR demonstrated a 55% depression of oxalate supported calcium uptake at 7.5 minutes which progressed to 87% at 30 minutes. At pH 6.4, control calcium uptake rates were significantly depressed accompanied by a further depression in the ischemic groups. Whole heart homogenate calcium uptakes mirrored the effects of the isolated SR. Calcium stimulated-Mg dependent ATPase activity was significantly depressed by both ischemia and acidosis with a decrease in the coupling ratio (μmoles Ca/μmoles ATP) at 15 and 30 minutes of ischemia. Acidosis (pH 6.4) significantly shifted the SR pCa-ATPase curve to the right increasing 50% activation from pCa 6.0 to 5.5 and depressing Vmax (pH 7.1 = 2.06 ± 0.14; pH 6.4 = 1.41 ± 0.05ymol Pi/mg-min; p < 0.01). With ischemia, there was a progressive decrease in maximal activation of the Ca2+ -ATPase enzyme and a shift in calcium sensitivity to a higher concentration. Hill plot analysis demonstrates a decrease in the Hill coefficient with ischemia. Steady-state calcium uptake, in the absence of oxalate demonstrated a similar depression following 7.5 minutes of ischemia at both pH 7.1 and 6.4. It is concluded that during short term, normothermic ischemia, there is significant and progressive sarcoplasmic reticulum dysfunction which is magnified at pH 6.4 characterized by a decrease in calcium uptake and ATPase activity which is due in part to a loss of enzyme activity and a probable increase in permeability of the SR membrane. It is postulated that during primary myocardial ischemia, this breakdown in sarcoplasmic reticulum function may serve as the source of intracellular calcium overload.


Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.


  1. 1.
    Nayler WG, Poole-Wilson PA, Williams A: Hypoxia and calcium. J Mol Cell Cardiol (11): 683–706, 1979.PubMedCrossRefGoogle Scholar
  2. 2.
    Zimmerman ANE, Dames W, Hulsmann WC, Snitder J, Wisse E, Durrer D: Morphological changes of heart muscle caused by successive perfusion with calcium-free and calcium containing solutions (calcium paradox). Cardiovasc Res (1):201–209, 1967.CrossRefGoogle Scholar
  3. 3.
    Hess ML, Krause SM, Greenfield LJ: Assessment of hypothermic, cardioplegic protection of the global ischemic canine myocardium. J Thorac Cardiovas Surg (80): 293–301, 1980.Google Scholar
  4. 4.
    Cobbe SM, Poole-Wilson PA: The time of onset and severity of acidosis in myocardial ischemia. J Mol Cell Cardiol (12): 745–760 1980.PubMedCrossRefGoogle Scholar
  5. 5.
    Fabiato A, Fabiato F: Contractions induced by a calcium-triggered release of calcium from the sarcoplasmic reticulum of single skinned cardiac cells. J Physiol (249): 469–495, 1975.PubMedCentralPubMedGoogle Scholar
  6. 6.
    McCallister LP, Daiello AC, Tyers GFO: Morpho-metric observations of the effects of normothermic ischemic arrest on dog myocardial ultrastructure. J Mol Cell Cardiol (10): 67–80, 1978.PubMedCrossRefGoogle Scholar
  7. 7.
    de Leiris J, Feuvray D: Ischemia-induced damage in the working rat heart preparation. The effect of perfusate substrate composition upon subendocardial ultrastructure of the ischemic left ventricular wall. J Mol Cell Cardiol (9): 365–373, 1977.PubMedCrossRefGoogle Scholar
  8. 8.
    Schwartz A, Wood JM, Allen JC, Burnet EP, Entman ML, Goldstein MA, Sordahl LA, Suzuki M: Alterations in energy metabolism and ultrastructure upon reperfusion of the ischemic myocardium after coronary occlusion. Am J Cardiol (36): 234–243, 1973.Google Scholar
  9. 9.
    Feher J, Briggs FN, Hess ML: Characterization of cardiac sarcoplasmic reticulum from ischemic myocardium: comparison of isolated sarcoplasmic reticulum with unfractionated homogenates. J Mol Cell Cardiol (12): 427–432, 1980.PubMedCrossRefGoogle Scholar
  10. 10.
    Garlick PB, Radda GK, Seeley PJ: Studies of acidosis in the ischemic heart by phosphorus nuclear magnetic resonance. Biochem J (184):547–554, 1979.PubMedCentralPubMedGoogle Scholar
  11. 11.
    Tait GA, Young RG, Wilson GJ, Steward DJ, MacGregor DC: Myocardial pH during regional ischemia: evaluation of a fiberoptic probe. Am J Physiol (243): H1027–H1031, 1982.PubMedGoogle Scholar
  12. 12.
    Cobbe SM, Poole-Wilson PA: Tissue acidosis in myocardial hypoxia. J Mol Cell Cardiol (12): 761–770, 1980.PubMedCrossRefGoogle Scholar
  13. 13.
    Mandel F, Kranias EG, Grassi de Gerde A, Sumida E, Schwartz A: The effects of pH on transient-state kinetics of Ca2+ - Mg2+ -ATPase of cardiac sarcoplasmic reticulum. Circ Res (50): 310–317, 1982.PubMedCrossRefGoogle Scholar
  14. 14.
    Fabiato A, Fabiato F: Effect of pH on the myofilaments and the sarcoplasmic reticulum of skinned cells from cardiac and skeletal muscles. J Physiol (276): 233–255, 1978.PubMedCentralPubMedGoogle Scholar
  15. 15.
    Hess ML, Warner MF, Robbins AD, Crute S, Greenfield LJ: Characterization of the excitation-contraction coupling system of the hypothermic myocardium following ischemia reperfusion. Cardiovas Res (15): 380–389, 1981.Google Scholar
  16. 16.
    Lowry OH, Rosenbrough AL, Farr AL, Randall RJ: Protein measurements with the folin phenol reagent. J Biol Chem (26): 267–275, 1951.Google Scholar
  17. 17.
    Penny CO: A simple microassay for inorganic phosphate. Anal Biochem (75): 201–210, 1976.CrossRefGoogle Scholar
  18. 18.
    Fabiato A, Fabiato F: Calcualtor programs for computing the composition of the solutions containing multiple metals and ligands used for experiments in skinned muscle cells. J Physiol, Paris (75): 463–505, 1979.Google Scholar
  19. 19.
    Fabiato A: Myoplasmic free calcium concentration reached during the twitch of an intact isolated cardiac cell and during calcium-induced release of calcium from the sarcoplasmic reticulum of a skinned cardiac cell from the adult rat or rabbit ventricle. J Gen Physiol (78): 457–497, 1981.PubMedCrossRefGoogle Scholar
  20. 20.
    Hess ML, Okabe E, Ash P, Kontos HA: Free radical mediation of the effects of acidosis on calcium transport by cardiac sarcoplasmic reticulum in whole heart homogenates. Cardiovas Res (In Press), 1983.Google Scholar
  21. 21.
    Hess ML, Okabe E, Kontos HA: Proton and oxygen free radical interaction with the calcium transport system of cardiac sarcoplasmic reticulum. J Mol Cell Cardiol (13): 767–772, 1981.PubMedCrossRefGoogle Scholar
  22. 22.
    Poole-Wilson PA: Effect of hypoxia and ischemia on calcium fluxes in rabbit myocardium. In Caldarera CM and Harris P (eds) Advances in studies on heart metabolism. CLUEB, Bologna, Italy, 1982, pp. 185–192.Google Scholar
  23. 23.
    Bourdillion PD, Poole-Wilson PA: The effects of verapamil, quiescence and cardioplegia on calcium exchange and mechanical function in ischemic rabbit myocardium. Circ Res (50): 360–368, 1982.CrossRefGoogle Scholar

Copyright information

© Martinus Nijhoff Publishing, Boston 1984

Authors and Affiliations

  • Michael L. Hess
  • Stephen M. Krause

There are no affiliations available

Personalised recommendations