Advertisement

On the Mechanism of Endogenous Lipolysis in Rat Heart: A Role of Lysosomes?

  • H. Stam
  • S. Broekhoven-Schokker
  • W. C. Hülsmann
Part of the NATO ASI Series book series (NSSA, volume 116)

Summary

Lipolytic activities of rat hearts towards full and partial glycerides were characterized. Our data indicate that the neutral triglyceride lipase (TGase) activity in heparin-preperfused hearts represents the intracellular precursor of vascular lipoprotein lipase (LPL). Upon subcellular fractionation the neutral TGase was recovered in the microsomal and cytosolic fraction. This neutral enzyme is distinct from the lysosomal acid TGase and the microsomal diglyceridase (DGase) and monoglyceridase (MGase) activity. Cycloheximide-induced inhibition of protein synthesis was accompanied by a sharp reduction in heparin-releasable LPL tissue neutral TGase activity, leaving the acid TGase, DGase and MGase activity unchanged. In cycloheximide-treated rat hearts, the basal and glucagon-stimulated release of glycerol was also not changed, ruling out a dominant role of the neutral tissue TGase in TG breakdown in heart. The myocardial lysosomal fraction appeared to be markedly enriched in triglycerides (TGs), while during prolonged perfusion a significant reduction could be observed in lysosomally recovered TGs. We propose that myocardial lipolysis predominantly proceeds by the the action of the lysosomal acid TGase in concert with the microsomal DGase and MGase activity.

Keywords

Lipase Activity Partial Glyceride Substrate Fatty Acid Acid Lipase Glycerol Release 
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.

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

References

  1. 1.
    J.R. Neely and H.F. Morgan, Relationship between carbohydrate and lipid metabolism and the energy balance of heart muscle, Annu. Rev. Physiol. 36: 413 (1974).CrossRefGoogle Scholar
  2. 2.
    A. Cryer, Tissue lipoprotein lipase activity and its action in lipoprotein metabolism, Int. J. Biochem. 13: 525 (1981).Google Scholar
  3. 3.
    Ts.-W. Wang, L.A. Menahan and J.I. Lech, Subcellular localization of marker enzymes, lipase and triglyceride in rat heart, J. Mol. Cell. Cardiol. 9: 25 (1977).PubMedCrossRefGoogle Scholar
  4. 4.
    H. Stan and W.C. Hülsmann, Erucic acid-induced alteration of cardiac triglycride hydrolysis, Lipids 15: 242 (1980).CrossRefGoogle Scholar
  5. 5.
    U. Pfeifer and P. Strauss, Autophagic vacuoles in heart muscle and liver. A comparative morphometric study including circadian variations in meal-fed rats, J. Mol. Cell. Cardiol. 7: 39 (1981).Google Scholar
  6. 6.
    W.C. Hülsmann, H. Stan and H. Jansen, Localization and function of myocardial lipolysis, Basic Res. Cardiol. 79: 268 (1984).CrossRefGoogle Scholar
  7. 7.
    H. Stan and W.C. Hülsmann, Effects of hormones, amino acids and specific inhibitors on rat heart heparin-releasable lipoprotein lipase and tissue neutral lipase activities during long-term perfusion. Biochim. Biophys. Acta 794: 72 (1984).CrossRefGoogle Scholar
  8. 8.
    H. Stan, S. Broekhoven-Schokker and W.C. Hülsmann, Characterization of mono-, di-and triacylglycerol lipase activities in the isolated rat heart, Biochim. Biophys. Acta, in the press.Google Scholar
  9. 9.
    H. Stan, S. Broekhoven-Schokker and W.C. Hülsmann, Studies on the involvement of lipolytic enzymes in endogenous lipolysis of the isolated rat heart, Biochim. Biophys. Acta, in the press.Google Scholar
  10. 10.
    K. Christiansen and P.K. Jensen, Membrane-bound lipid particles from beef heart. Chemical compositions, Biochim. Biophys. Acta 260: 449 (1972).CrossRefGoogle Scholar
  11. 11.
    F. Welman, D. Bowes and T.J. Peters, Electron microscopy of lysosomal fractions from guinea pig heart, J. Mol. Cell. Cardiol. 10: 527 (1978).PubMedCrossRefGoogle Scholar
  12. 12.
    H. Stan and W.C. Hülsmann, Regulation of lipases involved in the supply of subsrate fatty acids for the heart, Eur. Heart J. 6: 158 (1985).Google Scholar

Copyright information

© Plenum Press, New York 1986

Authors and Affiliations

  • H. Stam
    • 1
  • S. Broekhoven-Schokker
    • 1
  • W. C. Hülsmann
    • 1
  1. 1.Department of Biochemistry I, Medical FacultyErasmus University RotterdamRotterdamThe Netherlands

Personalised recommendations