title: Protective effect of eicosapentaenoic acid on ouabain toxicity in neonatal rat cardiac myocytes.
abstract: Isolated neonatal cardiac myocytes have been utilized as a model for the study of cardiac arrhythmogenic factors. The myocytes respond to the toxic effects of a potent cardiac glycoside, ouabain at 0.1 mM, by an increase in their spontaneous beating rate and a reduction in amplitude of contractions resulting within minutes in a lethal state of contracture. Incubating the isolated myocytes for 3-5 days in culture medium enriched with 5 microM arachidonic acid [20:4 (n-6)] had no effect on the development of lethal contracture after subsequent exposure to 0.1 mM ouabain. By contrast, incubating the myocytes for 3-5 days with 5 microM eicosapentaenoic acid [20:5 (n-3)] completely prevented the toxic effects of ouabain at 0.1 mM. There were no measurable differences in the degree to which ouabain inhibited Na,K-ATPase activity by comparing the control with the arachidonic acid- or the eicosapentaenoic acid-enriched myocytes. No differences in bumetanide-inhibitable 86Rb flux were observed between the three preparations. However, measurements with fura-2 of cytosolic free calcium levels indicated that control and arachidonic acid-enriched myocytes developed toxic cytosolic calcium concentrations of 845 +/- 29 and 757 +/- 64 nM, respectively, on exposure to 0.1 mM ouabain, whereas in eicosapentaenoic acid-enriched myocytes, physiologic calcium levels (214 +/- 29 nM) were preserved. Incubating the myocytes with eicosapentaenoic acid (5 microM) for 3-5 days resulted in a small reduction of arachidonic acid and a small but significant increase of eicosapentaenoic acid in membrane phospholipids of the myocytes.
authors.affiliation: Department of Preventive Medicine, Harvard Medical School, Massachusetts General Hospital, Boston 02114.
authors.forename: H
authors.initials: H
authors.lastname: Hallaq
authors.forename: A
authors.initials: A
authors.lastname: Sellmayer
authors.forename: T W
authors.initials: TW
authors.lastname: Smith
authors.forename: A
authors.initials: A
authors.lastname: Leaf
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D016718:Arachidonic Acid; D001095:Arachidonic Acids / Q000494:pharmacology; D001693:Biological Transport, Active / Q000187:drug effects; D002034:Bumetanide / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D015118:Eicosapentaenoic Acid / Q000494:pharmacology*; D005227:Fatty Acids / Q000032:analysis; D006321:Heart / Q000187:drug effects / Q000502:physiology*; D007700:Kinetics; D009200:Myocardial Contraction / Q000187:drug effects*; D010042:Ouabain / Q000494:pharmacology*; D010743:Phospholipids / Q000302:isolation & purification / Q000378:metabolism; D051381:Rats; D012413:Rubidium / Q000378:metabolism; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism
chemical_list: D001095:Arachidonic Acids; D005227:Fatty Acids; D010743:Phospholipids; D002034:Bumetanide; D016718:Arachidonic Acid; D010042:Ouabain; D015118:Eicosapentaenoic Acid; D000254:Sodium-Potassium-Exchanging ATPase; D012413:Rubidium; D002118:Calcium