Comparison of the effects of the ionophore salinomycin and adrenaline on the haemodynamics and work efficiency of the dog heart

Abstract

The positive inotropic, chronotropic, pressor, and coronary vasodilative effects of infused adrenaline (1 μg.kg⁻¹·min⁻¹) were compared with those of an intravenous injection of the carboxylic ionophore salinomycin (150 μg·kg^−l) in 10 dogs anaesthetised with pentobarbital. At doses normalised to produce a doubling of left ventricular dP/dt_max both drugs produced pronounced increases in blood pressure, cardiac output, and plasma catecholamine concentration and a small increase in heart rate. After 10 minutes of adrenaline infusion coronary artery blood flow doubled whereas salinomycin produced a sixfold increase, reflecting its specific coronary vasodilative properties. The increases in cardiac output and pressor, chronotropic, and inotropic actions of salinomycin were related to the release of endogenous catecholamines into the plasma by the ionophore, whereas the increase in coronary blood flow indicated a non-adrenergic relaxation of the coronary blood vessels. Calculated values of left ventricular hydraulic work appreciably increased with both drugs, but left ventricular oxygen consumption was much higher during adrenaline infusion than the peak effect obtained with salinomycin. Accordingly, the mechanical efficiency of the left ventricle was slightly decreased by adrenaline and doubled by salinomycin. Because of its favourable haemodynamic profile, salinomycin has potential as a drug for increasing cardiac output, blood pressure, and left ventricular force of contraction and for improving the myocardial blood perfusion and mechanical efficiency of the heart.