Summary
The myocardium contains diverse cellular components and heterogeneous phospholipid-containing membranes. The major phospholipids are phosphatidylcholine, phosphatidylethanolamine, phosphatidylinositnol, sphingomyelin, and cardiolipin. The phospholipases capable of hydrolyzing these membrane lipids include phospholipase A, lysophospholipase, and phosphatidylnositol-specific phospholipase C. Early studies revealed that myocardial phospholipase A with an acid pH is localized to lysosomes; those with more alkaline and neutral activities are present in cytosol, microsomes, mitochondria and sarcolemma. Recently, we have identified phosphatidylinositol-specific phospholipase C activity in bovine myocardium with molecular weights ranging from 40,000 to 271,000. Interestingly, forms I, II and III had pH optima ranging from 4.5 to 5,5; form III also had significant activity at pH 7.0. All activities were stimulated by calcium, suggesting that they are different from calcium-independent phospholipases C found in liver and brain. The pathophysiological significance of these four cytosolic forms of phospholipase C remains to be determined. Thus, under injury-promoting conditions, phospholipase C appears capable of hydrolyzing membrane-associated phosphatidylinositol and the polyphosphoinositides, whereas phospholipases A and lysosphospholiphases appear to prefer non-inositol containing phospholipids. Finally, very recent studies suggest “free radical-triggered lipolysis” by phospholipases as a possible mechnism for production of lysophospholipids in myocardial membranes.
Access this chapter
Tax calculation will be finalised at checkout
Purchases are for personal use only
Preview
Unable to display preview. Download preview PDF.
References
Weglicki WB, Owens K, Urschel CW, Sonnenblick EH (1973) In: Dhalla NS (ed) Myocardial metabolism. Recent Advances in Studies of Cardiac Structure and Metabolism, 3: 781–793
Weglicki WB, Waite BM, Sisson P, Shohet SB (1971) Myocardial phospholipase A of microsomal and mitochondrial fractions. Biochim Biophys Acta 231: 512–519
Weglicki WB, Waite BM, Stam AC (1972) Association of phospholipase A with the (Na++K+)Mg2+ ATPase of the myocardium. J Mol Cell Cardiol 4: 195–201
Franson RC, Waite BM, Weglicki WB (1972) Phospholipase A activity of lysosomes of rat myocardial tissue. Biochem 11: 472–476
Weglicki WB, Owens K, Ruth RC, Sonnenblick EH (1974) Activity of endogenous myocardial lipases during incubation at acid pH. Cardiovasc Res 8: 237–242
Low MG, Weglicki WB (1983) Resolution of myocardial phospholipase C into several forms with distinct properties. Biochem J 215: 325–334
Weglicki WB, Dickens BF, Mak IT (1984) Enhanced lysosomal phospholipid degradation and lysophospholipid production due to free radicals. Biochem Biophys Res Commun 126: 229–235
Weglicki WB, Ruth RC, Owens K, Griffin H, Waite BM (1974) Acid-active phospholipases and neutral lipid lipases: Changes in lipid composition of triton-filled lysosomes during lysis. Biochim Biophys Acta 337: 145–152
Mak IT, Kramer JH, Weglicki WB (1986) Potentiation of free radical-induced peroxidative injury to sarcolemmal membranes by lipid amphiphiles. J Biol Chem 261: 1153–1157
Author information
Authors and Affiliations
Editor information
Rights and permissions
Copyright information
© 1987 Springer-Verlag Berlin Heidelberg
About this paper
Cite this paper
Weglicki, W.B., Low, M.G. (1987). Phospholipases of the myocardium. In: Stam, H., van der Vusse, G.J. (eds) Lipid metabolism in the normoxic and ischaemic heart. Steinkopff, Heidelberg. https://doi.org/10.1007/978-3-662-08390-1_13
Download citation
DOI: https://doi.org/10.1007/978-3-662-08390-1_13
Publisher Name: Steinkopff, Heidelberg
Print ISBN: 978-3-662-08392-5
Online ISBN: 978-3-662-08390-1
eBook Packages: Springer Book Archive