Abstract
Using the redox potential of the myocardium ( ?? Eh) as a measure of the myocardial energy metabolism. the metabolic effects of three representative catecholamines, adrenaline (Adr). noradrenaline (Nor) and isoproterenol (Isp) were studied, in the canine heart-lung preparation supported by a donor. Adr and Nor produced an initial improvement of ?? Lh, followed by a sustained debasement, while Isp produced only a debasement. Pretreatment of the preparation with phentolamine or dibenamine, resulted in an abolishment of the initial irniprovement, while the effect of Isp remained unchanged. After pretreatment of the preparation with practolol, the positive inotropic and chronotropic effect and the associated increase in the myocardial oxygen consumption were no longer seen with all the catecholamines tested. Under these conditions. Adr and Nor produced a sustained improvement of ?? Lh, while Isp produced a transient debasement, which, in turn, was abolished by propranolol. When the heart was driven at a constant rate, the myocardial oxygen consumption did not increase with the catecholamines in most of the cases and a sustained improvement of ?? Eh was observed with Adr and Nor: Isp produced a transient debasement. These findings indicate that catecholamines produce an improvement of the myocardial energy metabolism through activation of the adrenergic α-receptor.
