Effects of norepinephrine infusion on myocardial high-energy phosphate content and turnover in the living rat.
Using 31P-nuclear magnetic resonance, we studied the relationship between myocardial high-energy phosphate content and flux values for the creatine kinase reaction in the living rat under inotropic states achieved during norepinephrine infusion and halothane anesthesia. Under 2% halothane anesthesia (n = 4), 1% halothane anesthesia (n = 5) and norepinephrine infusion (n = 4), rats developed rate-pressure products of 19.5 +/- 1.6, 32.0 +/- 3.5, and 48.5 +/- 2.0 X 1,000 mmHg/min, respectively. Adenosine triphosphate content was not affected by inotropic state, ranging from 24.3 +/- 1.1 to 25.6 +/- 1.1 mumol/g dry weight, but creatine phosphate content varied inversely and reversibly with cardiac performance from 45.6 +/- 6.0 under 2% halothane to 26.0 +/- 6.5 mumol/g dry weight during norepinephrine infusion. The flux values for the creatine kinase reaction were 15.4 +/- 4.6, 20.5 +/- 2.0, and 30.1 +/- 7.9 mumol/g dry weight per s under 2% halothane, 1% halothane, and 1% halothane with norepinephrine, respectively. These results suggest that the turnover of myocardial high-energy phosphate compounds, not their tissue contents, matches cardiac performance during inotropic stimulation.
D000255:Adenosine Triphosphate / Q000032:analysis*; D000818:Animals; D002304:Cardiac Pacing, Artificial; D003402:Creatine Kinase / Q000378:metabolism; D004347:Drug Interactions; D006221:Halothane / Q000494:pharmacology; D006321:Heart / Q000187:drug effects*; D006439:Hemodynamics / Q000187:drug effects*; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D009206:Myocardium / Q000378:metabolism*; D009638:Norepinephrine / Q000494:pharmacology*; D010725:Phosphocreatine / Q000032:analysis*; D051381:Rats; D011919:Rats, Inbred Strains
D010725:Phosphocreatine; D000255:Adenosine Triphosphate; D003402:Creatine Kinase; D006221:Halothane; D009638:Norepinephrine