Heart and Vessels

, Volume 2, Issue 1, pp 6–14 | Cite as

The effects of raised phosphate level on the energy metabolism, contractile function, and fine structure of oxygenated and oxygen-deficient myocardium

  • Lois C. Armiger
  • Stuart M. Humphrey
  • Elizabeth J. N. West
  • Catherine M. Knell
Originals

Summary

The possible role of inorganic phosphate (Pi) in depressing the contractility of oxygen-deficient myocardium was investigated by examining the effects of 30 mM Pi on the cardiac function and myocardial biochemistry and fine structure in normoxic and anoxic Langendorff-perfused isolated rat hearts. In normoxia, the intracellular Pi level increased three-fold, the ATP content remained normal, and there was moderate loss of glycogen only. Contractile performance (as assessed from systolic pressure recordings) was significantly depressed, as was the heart rate for the first 10 min. The myocardial fine structure showed persistent glycogen, marked relaxation of myofibrils, and a higher incidence of vacuolation than in hearts with normal Pi. In anoxia, the intracellular Pi level was comparable with that of the perfusate and both ATP and glycogen were severely depleted. Contractile performance and heart beat ceased completely at 15 min, although in anoxic controls both persisted at low levels for at least 25 min. In anoxia, Pi also depressed coronary flow rate. In the inner half of the ventricular wall of oxygen-depleted hearts, where flow became reduced after 15 or more min, Pi markedly reduced the formation of intramitochondrial densities and augmented mitochondrial swelling and ischaemic contracture, which extended out through the mid-myocardium. In the outer half of the wall, where flow remained high, it promoted severe dilatation of the sarcoplasmic reticulum vesicles and undifferentiated regions of the intercalated discs. The observed effects in normoxia are probably attributable at least in part to the lowering of the free Ca2+ concentration of the perfusate by the increased Pi level. The effects in anoxia may be related chiefly to the critical reduction of available intracellular Ca2+ and the more rapid and extensive development of ischaemic contracture.

Key words

Inorganic phosphate Normoxia/anoxia ATP Glycogen Cardiac function Electron microscopy 

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Copyright information

© Springer-Verlag 1986

Authors and Affiliations

  • Lois C. Armiger
    • 1
  • Stuart M. Humphrey
    • 1
  • Elizabeth J. N. West
    • 1
  • Catherine M. Knell
    • 1
  1. 1.Department of PathologyUniversity of Auckland School of MedicineAucklandNew Zealand

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