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Cardiology Unit, University of Vermont, Burlington, Vermont 05401
Submitted 23 August 2002 ; accepted in final form 23 May 2003
The effects of endothelin (ET) receptor blockade on energy utilization in heart failure (HF) are unknown. We administered ET type A (ETA), ET type B (ETB), and ETA/ETB antagonists to isolated hearts from Dahl salt-sensitive (DS) rats with HF and controls. Contractile efficiency was assessed as slope1 of myocardial O consumption (
O2)-pressure-volume area relation. In HF, ETA and ETA/ETB but not ETB blockade decreased the contractility index (Emax)(15 ± 3% and 17 ± 2%, P < 0.05), excitation-contraction (E-C) coupling
O2 (39 ± 4% and 37 ± 5%, P < 0.01), and efficiency (15 ± 4% and 17 ± 2%, P < 0.05). Despite decreased efficiency, ETA and ETA/ETB blockade decreased total
O2 (24 ± 3% and 22 ± 2%, P < 0.05). Na+/H+ exchanger inhibition decreased Emax and E-C coupling
O2 similar to ETA and ETA/ETB blockade, but did not alter efficiency. In HF, endogenous ET-1 maintains contractility at expense of increased
O2 through ETA receptor activation, likely mediated by Na+/H+ exchange.
oxygen consumption
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