Evaluation by 31P NMR of the effects of acebutolol on the ischaemic isolated rat heart.

We used 31P NMR spectroscopy to study the effect of acebutolol on the metabolic disturbances caused by ischaemia in the isolated rat heart. The intracellular acidosis and high-energy phosphate compound depletion induced by global low-flow ischaemia were significantly attenuated in the presence of acebutolol 2.7 X 10(-5) and 1.35 X 10(-4) M. The drug displayed no significant effect either at the 5.4 X 10(-6) M concentration or when administered as pretreatment to the animals (50 mg X kg-1, 120 and 60 min before isolating the heart). Since acebutolol had no effect on the contractility of the isolated rat heart at the 2.7 X 10(-5) M concentration the present results suggest that the mechanisms through which acebutolol exerts its effects on energy metabolism are not related to a reduction of cardiac work. The possible contribution of the membrane-stabilizing property of the drug is suggested by the fact that high concentrations are needed and that a short pretreatment had no effect.