title: Functional and energetic consequences of chronic myocardial creatine depletion by beta-guanidinopropionate in perfused hearts and in intact rats.
abstract: Oral feeding with the creatine analogue beta-guanidinopropionate (beta-GP) reduces myocardial phosphocreatine and creatine concentrations by about 80%in vitro, this is accompanied by reduced contractile performance. We hypothesized, thus, that beta-GP feeding leads to hemodynamic changes in vivo characteristic of heart failure. beta-GP was fed to Wistar rats for up to 8 weeks. In isolated hearts, function was measured isovolumically, myocardial energetics were followed with (31)P-NMR spectroscopy. In vivo hemodynamics were measured with Millar-Tip-catheters and an electromagnetic flow probe. Beta-GP feeding did not alter heart weight. In vitro, diastolic pressure-volume curves indicated structural left ventricular dilatation, and a 36% reduction of left ventricular developed pressure was found; phosphocreatine was reduced by approximately 80%, ATP unchanged and creatine kinase reaction velocity ((31)P-MR saturation transfer) decreased by approximately 90%. The total creatine pool (high-pressure liquid chromatography) was reduced by up to approximately 70%. In contrast to in vitro findings, in vivo cardiac hemodynamics (including left ventricular developed pressure, d P/d t(max), cardiac output and peripheral vascular resistance) at rest and during acute volume loading showed no alterations after beta-GP feeding. The only functional impairment observed in vivo was a 14% reduction of maximum left ventricular developed pressure during brief aortic occlusion. In the intact rat, cardiac and/or humoral compensatory mechanisms are sufficient to maintain normal hemodynamics in spite of a 90% reduction of creatine kinase reaction velocity. However, chronic beta-GP feeding leads to structural left ventricular dilatation.
authors.affiliation: The Theodor-Boveri-Institut für Biowissenschaften, Universität Würzburg, Germany.
authors.forename: S
authors.initials: S
authors.lastname: Neubauer
authors.forename: K
authors.initials: K
authors.lastname: Hu
authors.forename: M
authors.initials: M
authors.lastname: Horn
authors.forename: H
authors.initials: H
authors.lastname: Remkes
authors.forename: K D
authors.initials: KD
authors.lastname: Hoffmann
authors.forename: C
authors.initials: C
authors.lastname: Schmidt
authors.forename: T J
authors.initials: TJ
authors.lastname: Schmidt
authors.forename: K
authors.initials: K
authors.lastname: Schnackerz
authors.forename: G
authors.initials: G
authors.lastname: Ertl
mesh_terms: D000244:Adenosine Diphosphate / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D003326:Coronary Circulation / Q000187:drug effects; D003401:Creatine / Q000378:metabolism*; D003971:Diastole; D006146:Guanidines / Q000494:pharmacology*; D006321:Heart / Q000187:drug effects / Q000502:physiology*; D006339:Heart Rate / Q000187:drug effects; D006439:Hemodynamics / Q000187:drug effects* / Q000502:physiology; D009682:Magnetic Resonance Spectroscopy; D009206:Myocardium / Q000378:metabolism*; D009929:Organ Size / Q000187:drug effects; D010477:Perfusion; D010725:Phosphocreatine / Q000378:metabolism; D011422:Propionates / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D013997:Time Factors; D016277:Ventricular Function, Left / Q000187:drug effects
chemical_list: D006146:Guanidines; D011422:Propionates; D010725:Phosphocreatine; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D003401:Creatine; C005775:guanidinopropionic acid