Effects of isoproterenol, propranolol and artificial pacing on hemodynamics and energy liberation of the infarcted heart in dogs.

As reported previously, oxidative phosphorylation was uncoupled in the infarcted canine heart muscle. In this study, it was revealed that the heart rate increased and the left ventricular isometric time tension index was deteriorated in experimental coronary ligation in dogs. Isoproterenol infusion before and after coronary ligation modified hemodynamic changes due to coronary occlusion. Mitochondria from the infarcted myocardium of the isoproterenol treated dog showed uncoupling of oxidative phosphorylation as same as cases of coronary ligation without isoproterenol treatment. By injection of propranolol prior to coronary oxidative phosphorylation in the infarcted myocardium was mitigated, followed by decreased mitochondrial oxygen consumption rates. With artificial pacing before and after coronary ligation, oxidative phosphorylation was still uncoupled when the pacing rate was made frequent while it was less uncoupled when the contraction rate was decreased. It might be considered that uncoupling of oxidative phosphorylation in the infarcted myocardium was enhanced in the state of enforced increment of chronotropism and inotropism while it was rather protected inthe state of moderate cardiac suppression. Energy liberation in the infarcted heart may be affected by changes of hemodynamics.