| Autor: |
Duncker DJ; Divison of Experimental Cardiology, Department of Cardiology, Thorax Center, Erasmus Medical Center, University Medical Center Rotterdam, Rotterdam, The Netherlands., Sorop O; Divison of Experimental Cardiology, Department of Cardiology, Thorax Center, Erasmus Medical Center, University Medical Center Rotterdam, Rotterdam, The Netherlands., van de Wouw J; Divison of Experimental Cardiology, Department of Cardiology, Thorax Center, Erasmus Medical Center, University Medical Center Rotterdam, Rotterdam, The Netherlands., Fen G; Divison of Experimental Cardiology, Department of Cardiology, Thorax Center, Erasmus Medical Center, University Medical Center Rotterdam, Rotterdam, The Netherlands., de Beer VJ; Divison of Experimental Cardiology, Department of Cardiology, Thorax Center, Erasmus Medical Center, University Medical Center Rotterdam, Rotterdam, The Netherlands., Taverne YJ; Divison of Experimental Cardiology, Department of Cardiology, Thorax Center, Erasmus Medical Center, University Medical Center Rotterdam, Rotterdam, The Netherlands., de Graaff HJD; Divison of Experimental Cardiology, Department of Cardiology, Thorax Center, Erasmus Medical Center, University Medical Center Rotterdam, Rotterdam, The Netherlands., Merkus D; Divison of Experimental Cardiology, Department of Cardiology, Thorax Center, Erasmus Medical Center, University Medical Center Rotterdam, Rotterdam, The Netherlands.; Walter Brendel Center of Experimental Medicine, LMU Munich, Munich, Germany.; German Center for Cardiovascular Research, Partner Site Munich, Munich Heart Alliance, Munich, Germany. |
| Abstrakt: |
The interplay of mechanisms regulating coronary blood flow (CBF) remains incompletely understood. Previous studies in dogs indicated that CBF regulation by K ATP channels, adenosine, and nitric oxide (NO) follows a nonlinear redundancy design and fully accounted for exercise-induced coronary vasodilation. Conversely, in swine, these mechanisms appear to regulate CBF in a linear additive fashion with considerable exercise-induced vasodilation remaining when all three mechanisms are inhibited. A direct comparison between these studies is hampered by the different doses and administration routes (intravenous vs. intracoronary) of drugs inhibiting these mechanisms. Here, we investigated the role of K ATP channels, adenosine, and NO in CBF regulation in swine using identical drug regimen as previously employed in dogs. Instrumented swine were exercised on a motor-driven treadmill, before and after blockade of K ATP channels (glibenclamide, 50 µg/kg/min ic) and combination of inhibition of NO synthase ( N ω -nitro-l-arginine, NLA, 1.5 mg/kg ic) and adenosine receptors (8-phenyltheophylline, 8PT, 5 mg/kg iv) or their combination NLA + 8PT + glibenclamide. Glibenclamide and NLA + 8PT each produced coronary vasoconstriction both at rest and during exercise, whereas the combination of NLA + 8PT + glibenclamide resulted in a small further coronary vasoconstriction compared with NLA + 8PT that was, however, less than the sum of the vasoconstriction produced by NLA + 8PT and glibenclamide, each. Thus, in contrast to previous observations in the dog, 1 ) the coronary vasoconstrictor effect of glibenclamide was not enhanced in the presence of NLA + 8PT and 2 ) the exercise-induced increase in CBF was largely maintained. These findings show profound species differences in the mechanisms controlling CBF at rest and during exercise. NEW & NOTEWORTHY The present study demonstrates important species differences in the regulation of coronary blood flow by adenosine, NO, and K ATP channels at rest and during exercise. In swine, these mechanisms follow a linear additive design, as opposed to dogs which follow a nonlinear redundant design. Simultaneous blockade of all three mechanisms virtually abolished exercise-induced coronary vasodilation in dogs, whereas a substantial vasodilator reserve could still be recruited during exercise in swine. |
