6533b825fe1ef96bd1281d15

RESEARCH PRODUCT

Die Wirkung von Ouabain auf die Elimination von Noradrenalin aus der Perfusionsfl�ssigkeit des isolierten Kaninchenherzens

subject

description

Isolated rabbit hearts were perfused with Tyrode solution containing 10 ng/ml (-)-noradrenaline for 20 min. The uptake by the heart of noradrenaline was calculated by estimating the percentage of amine removed from the perfusion fluid during a single passage through the heart. Previous experiments have shown that the amount of noradrenaline removed from the perfusion fluid corresponds well to the amount retained by the heart. In control experiments, the mean removal (elimination) of noradrenaline was 50±1.7% of the amount infused as measured biologically and 46±2.2% as measured fluorimetrically. Ouabain was added to the perfusion fluid at concentrations ranging from 2.74·10−7 to 2.0·10−6 mol/l. The lowest dose caused a positive inotropic effect. With higher concentrations of ouabain there was a transitory increase in contractile force which was followed by a negative inotropic action, atrioventricular block and contracture of the myocardium. The noradrenaline uptake by the heart was neither affected by “therapeutic” nor by “toxic” concentrations of ouabain. On the other hand, almost complete inhibition of noradrenaline uptake was found after administration of 3·10−5 mol/l cocaine. It is concluded that in the isolated heart ouabain does not interfere with noradrenaline transport across the cell membrane although the concentrations of ouabain employed are known to inhibit active transport of sodium and potassium.