title: Activation time of myocardial oxidative phosphorylation in creatine kinase and adenylate kinase knockout mice.
abstract: Our goal was to determine whether mice genetically altered to lack either creatine kinase (M/MtCK(-/-)) or adenylate kinase (AK(-/-)) show altered properties in the dynamic regulation of myocardial oxygen consumption (MVO(2)). We measured contractile function, oxygen consumption, and the mean response time of oxygen consumption to a step increase in heart rate [i.e., mitochondrial response time (t(mito))] in isolated Langendorff-perfused hearts from wild-type (n = 6), M/MtCK(-/-) (n = 6), and AK(-/-) (n = 4) mice. Left ventricular developed pressure was higher in M/MtCK(-/-) hearts (88.2 +/- 6.8 mmHg) and lower in AK(-/-) hearts (46.7 +/- 9.4 mmHg) compared with wild-type hearts (60.7 +/- 10.1 mmHg) at the basal pacing rate. Developed pressure fell slightly when heart rate was increased in all three groups. Basal MVO(2) at 300 beats/min was 19.1 +/- 2.4, 19.4 +/- 1.5, and 16.3 +/- 1.9 micromol x min(-1) x g dry wt(-1) for M/MtCK(-/-), AK(-/-), and wild type, respectively, which increased to 25.5 +/- 3.7, 25.4 +/- 2.6, and 22.0 +/- 2.6 micromol. min(-1) x g(-1), when heart rate was increased to 400 beats/min. The t(mito) was significantly faster in M/MtCK(-/-) hearts: 3.0 +/- 0.3 versus 7.3 +/- 0.6 and 8.0 +/- 0.4 s for M/MtCK(-/-), AK(-/-), and wild-type hearts, respectively. Our results demonstrate that MVO(2) of M/MtCK(-/-) hearts adapts more quickly to an increase in heart rate and thereby support the hypothesis that creatine kinase acts as an energy buffer in the cytosol, which delays the energy-related signal between sites of ATP hydrolysis and mitochondria.
authors: Laboratory for Physiology, Institute for Cardiovascular Research, Vrije Universiteit, 1081 BT Amsterdam, The Netherlands. hvanbeek@bio.vu.nl
authors: Lori A
authors: LA
authors: Gustafson
authors: Johannes H G M
authors: JH
authors: Van Beek
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000263:Adenylate Kinase / Q000172:deficiency* / Q000502:physiology; D000818:Animals; D003402:Creatine Kinase / Q000172:deficiency* / Q000502:physiology; D005260:Female; D006339:Heart Rate; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008929:Mitochondria, Heart / Q000378:metabolism; D009206:Myocardium / Q000378:metabolism* / Q000648:ultrastructure; D010085:Oxidative Phosphorylation; D010101:Oxygen Consumption; D013997:Time Factors; D016277:Ventricular Function, Left; D017725:Ventricular Pressure
chemical_list: D000255:Adenosine Triphosphate; D003402:Creatine Kinase; D000263:Adenylate Kinase