title: Erythropoietin induces positive inotropic and lusitropic effects in murine and human myocardium.
abstract: Initial clinical studies indicate a potential beneficial effect of erythropoietin (EPO) in patients with anemia and heart failure. Here, we investigate the direct contractile effects of erythropoietin on myocardial tissue. Treatment with EPO (50U/mL) using excitable murine and human left ventricular muscle preparations resulted in a 37% and 62% increase in twitch tension, respectively (P<0.05). Isolated murine cardiomyocytes exposed to EPO demonstrated a 41% increase in peak sarcomere shortening (P=0.012). Using compounds that specifically stimulate a non-erythropoietic EPO receptor yielded similar increases in contractile dynamics. Cardiomyocyte Ca(2+)dynamics showed an 18% increase in peak calcium in EPO treated cardiomyocytes over controls (P=0.03). Studies in muscle strips skinned after EPO treatment demonstrated a phosphorylation dependant increase in the viscous modulus as well as an increase in oscillatory work. The EPO mediated increase in peak sarcomere shortening was abrogated by PI3-K blockade via wortmannin and by non-isozyme specific PKC blockade by chelerythrine. Finally, EPO treatment resulted in an increase in PKCε in the particulate cellular fraction, indicating activation of this isoform. EPO exhibits direct positive inotropic and lusitropic effects in cardiomyocytes and ventricular muscle preparation. These effects are mediated through PI3-K and PKCε isoform signaling to directly affect both calcium release dynamics and myofilament function.
authors: The Department of Medicine (Cardiac Unit), University of Vermont, College of Medicine, Burlington, VT, USA.
authors: David
authors: D
authors: Hefer
authors: Ting
authors: T
authors: Yi
authors: Donald E
authors: DE
authors: Selby
authors: David E
authors: DE
authors: Fishbaugher
authors: Sarah M
authors: SM
authors: Tremble
authors: Kelly J
authors: KJ
authors: Begin
authors: Prospero
authors: P
authors: Gogo
authors: Martin M
authors: MM
authors: Lewinter
authors: Markus
authors: M
authors: Meyer
authors: Bradley M
authors: BM
authors: Palmer
authors: Peter
authors: P
authors: Vanburen
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism; D002316:Cardiotonic Agents / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation / Q000187:drug effects; D004921:Erythropoietin / Q000378:metabolism / Q000494:pharmacology*; D006321:Heart / Q000187:drug effects*; D006801:Humans; D066298:In Vitro Techniques; D051379:Mice; D009200:Myocardial Contraction / Q000187:drug effects*; D009206:Myocardium / Q000378:metabolism*; D032383:Myocytes, Cardiac / Q000187:drug effects; D010210:Papillary Muscles / Q000187:drug effects; D011493:Protein Kinase C / Q000378:metabolism; D017467:Receptors, Erythropoietin / Q000819:agonists / Q000737:chemistry; D015398:Signal Transduction
chemical_list: D002316:Cardiotonic Agents; D017467:Receptors, Erythropoietin; D004921:Erythropoietin; D011493:Protein Kinase C; D002118:Calcium