Beneficial effect of practolol in preventing adrenaline-induced systemic and myocardial metabolic changes

The aim of the study was to investigate whether the beta blocking agent, practolol, is able to modify some of the metabolic and hormonal responses and the local myocardial changes evoked by an excess of adrenaline similar to that seen after acute coronary occlusion. Adrenaline (1.2 micrograms/kg/min) and practolol (1 mg/kg) were infused concurrently to anaesthetized intact dogs for 5 h. Blood free fatty acid and triiodothyronine levels were measured initially and after 2, 4 and 5 h of infusion. At the end of the infusion the myocardium was subjected to biochemical, histoenzymatic and electron microscopic examination. The results were compared with those obtained in dogs infused with adrenaline alone and with saline alone. Practolol reduced the adrenaline-induced increase in free fatty acids and a fall in triiodothyronine in the blood. Myocardial acetate accumulation and ATP decrease were both reduced by practolol. Histoenzymatic and electron microscopic changes were less. These effects of practolol upon systemic and myocardial disturbances induced by the excess of adrenaline indicate that it might be effective in modifying any excessive adrenergic response which may occur in acute myocardial infarction.