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Article: Phosphatidylcholine metabolism in isolated rat heart: Modulation by ethanol and vitamin E

TitlePhosphatidylcholine metabolism in isolated rat heart: Modulation by ethanol and vitamin E
Authors
Issue Date1989
Citation
Biochimica Et Biophysica Acta - Lipids And Lipid Metabolism, 1989, v. 1005 n. 3, p. 225-232 How to Cite?
AbstractProlonged ethanol administration has been reported to cause defects in cardiac performance and abnormal cardiac lipid contents. However, little is known regarding the short-term administration of ethanol to the perfused heart and its effect on cardiac phospholipid metabolism. In this study, the isolated Langendorff heart perfusion was used as a model to study the effects of ethanol and a combination of ethanol and vitamin E (DL-α-tocopherol) on phospholipid metabolism. When perfused with 1% ethanol for 4 h, the major cardiac phospholipids were not altered but a 60% increase in lysophosphatidylcholine level was observed. Studies on the lysophosphatidylcholine metabolic enzymes revealed that phospholipase A (both phospholipase A1 and A2) activity was enhanced in the ethanol-perfused heart, but lysophospholipase and acyltransferase activities were unaffected by ethanol treatment. When the heart was perfused with 1% ethanol in the presence of 50-100 μM vitamin E, the ethanol-induced lysophosphatidylcholine accumulation was completely abolished. This was largely attributed to the attenuation of phospholipase A activities by vitamin A. In order to delineate the opposing effects of ethanol and vitamin E on phospholipid metabolism in the heart, phospholipase A activities in the subcellular fractions were determined in the presence of 0.5-2.0% ethanol or a combination of 1% ethanol and 0-100 μM vitamin E. Ethanol alone exhibited a biphasic effect on phospholipase A activity with maximum stimulation of enzyme activities at 1% concentration. When phospholipase A was assayed in 1% ethanol and vitamin E (25-100 μM), its activity was inhibited by vitamin E in a dose-dependent manner. The mechanism by which ethanol enhanced phospholipase A activities was further investigated with a partially purified enzyme from the rat heart cytosol. Kinetic studies with different concentrations of phosphatidylcholine revealed that at low substrate concentrations, ethanol was inhibitory to the reaction, whereas at high substrate concentrations, the reaction was enhanced by ethanol. Vitamin E (50 μM) completely abolished the ethanol-induced enhancement of enzyme activity in a noncompetitive manner. Since lysophosphatidylcholine is cytolytic at high concentration and its accumulation in the heart has been postulated as a biochemical cause of cardiac dysfunction, the level of the lysolipid in the heart must be under rigid control. Our result suggest that the modulation of cardiac phospholipase A activity is an important mechanism for the regulation of lysophosphatidylcholine levels in the rat heart.
Persistent Identifierhttp://hdl.handle.net/10722/170943
ISSN
2000 Impact Factor: 2.973
ISI Accession Number ID

 

DC FieldValueLanguage
dc.contributor.authorChoy, PCen_US
dc.contributor.authorO, Ken_US
dc.contributor.authorRicky, KOen_US
dc.contributor.authorMan, RYKen_US
dc.contributor.authorChan, ACen_US
dc.date.accessioned2012-10-30T06:11:32Z-
dc.date.available2012-10-30T06:11:32Z-
dc.date.issued1989en_US
dc.identifier.citationBiochimica Et Biophysica Acta - Lipids And Lipid Metabolism, 1989, v. 1005 n. 3, p. 225-232en_US
dc.identifier.issn0005-2760en_US
dc.identifier.urihttp://hdl.handle.net/10722/170943-
dc.description.abstractProlonged ethanol administration has been reported to cause defects in cardiac performance and abnormal cardiac lipid contents. However, little is known regarding the short-term administration of ethanol to the perfused heart and its effect on cardiac phospholipid metabolism. In this study, the isolated Langendorff heart perfusion was used as a model to study the effects of ethanol and a combination of ethanol and vitamin E (DL-α-tocopherol) on phospholipid metabolism. When perfused with 1% ethanol for 4 h, the major cardiac phospholipids were not altered but a 60% increase in lysophosphatidylcholine level was observed. Studies on the lysophosphatidylcholine metabolic enzymes revealed that phospholipase A (both phospholipase A1 and A2) activity was enhanced in the ethanol-perfused heart, but lysophospholipase and acyltransferase activities were unaffected by ethanol treatment. When the heart was perfused with 1% ethanol in the presence of 50-100 μM vitamin E, the ethanol-induced lysophosphatidylcholine accumulation was completely abolished. This was largely attributed to the attenuation of phospholipase A activities by vitamin A. In order to delineate the opposing effects of ethanol and vitamin E on phospholipid metabolism in the heart, phospholipase A activities in the subcellular fractions were determined in the presence of 0.5-2.0% ethanol or a combination of 1% ethanol and 0-100 μM vitamin E. Ethanol alone exhibited a biphasic effect on phospholipase A activity with maximum stimulation of enzyme activities at 1% concentration. When phospholipase A was assayed in 1% ethanol and vitamin E (25-100 μM), its activity was inhibited by vitamin E in a dose-dependent manner. The mechanism by which ethanol enhanced phospholipase A activities was further investigated with a partially purified enzyme from the rat heart cytosol. Kinetic studies with different concentrations of phosphatidylcholine revealed that at low substrate concentrations, ethanol was inhibitory to the reaction, whereas at high substrate concentrations, the reaction was enhanced by ethanol. Vitamin E (50 μM) completely abolished the ethanol-induced enhancement of enzyme activity in a noncompetitive manner. Since lysophosphatidylcholine is cytolytic at high concentration and its accumulation in the heart has been postulated as a biochemical cause of cardiac dysfunction, the level of the lysolipid in the heart must be under rigid control. Our result suggest that the modulation of cardiac phospholipase A activity is an important mechanism for the regulation of lysophosphatidylcholine levels in the rat heart.en_US
dc.languageengen_US
dc.relation.ispartofBiochimica et Biophysica Acta - Lipids and Lipid Metabolismen_US
dc.subject.meshAcyltransferases - Metabolismen_US
dc.subject.meshAnimalsen_US
dc.subject.meshEthanol - Pharmacologyen_US
dc.subject.meshHeart - Drug Effectsen_US
dc.subject.meshKineticsen_US
dc.subject.meshLysophospholipase - Metabolismen_US
dc.subject.meshMaleen_US
dc.subject.meshMultienzyme Complexes - Metabolismen_US
dc.subject.meshMyocardium - Metabolismen_US
dc.subject.meshPerfusionen_US
dc.subject.meshPhosphatidylcholines - Metabolismen_US
dc.subject.meshPhospholipases A - Metabolismen_US
dc.subject.meshPhospholipases A1en_US
dc.subject.meshPhospholipids - Isolation & Purification - Metabolismen_US
dc.subject.meshRatsen_US
dc.subject.meshRats, Inbred Strainsen_US
dc.subject.meshSubcellular Fractions - Metabolismen_US
dc.subject.meshVitamin E - Pharmacologyen_US
dc.titlePhosphatidylcholine metabolism in isolated rat heart: Modulation by ethanol and vitamin Een_US
dc.typeArticleen_US
dc.identifier.emailMan, RYK:rykman@hkucc.hku.hken_US
dc.identifier.authorityMan, RYK=rp00236en_US
dc.description.naturelink_to_subscribed_fulltexten_US
dc.identifier.doi10.1016/0005-2760(89)90041-6-
dc.identifier.pmid2804051-
dc.identifier.scopuseid_2-s2.0-0024464941en_US
dc.identifier.volume1005en_US
dc.identifier.issue3en_US
dc.identifier.spage225en_US
dc.identifier.epage232en_US
dc.identifier.isiWOS:A1989AV54800004-
dc.identifier.scopusauthoridChoy, PC=7006633002en_US
dc.identifier.scopusauthoridO, K=7006328603en_US
dc.identifier.scopusauthoridRicky, KO=6504186569en_US
dc.identifier.scopusauthoridMan, RYK=7004986435en_US
dc.identifier.scopusauthoridChan, AC=7403168442en_US

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