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  • Title: Exercise induced changes of catecholamines and potassium in plasma of dogs after treatment with propranolol.
    Author: Staib AH, Appel E, Starey F, Lindner E, Grötsch H, Palm D, Grobecker H.
    Journal: Arzneimittelforschung; 1980; 30(9):1514-7. PubMed ID: 7193019.
    Abstract:
    Previous studies in man have shown that during beta-adrenoceptor blockade physical exercise caused a significantly greater elevation of plasma catecholamines than without blockade. After blockade of beta-adrenoceptors, increased levels of circulating catecholamines should have an unopposed effect on adrenergic alpha-receptors. In order to elucidate such an effect, experiments were performed with 7 trained dogs before and after acute beta-adrenoceptor blockade (0.1 mg/kg (-)-propranolol i. v.). Exercise was performed on a conveyor (10 min, 10 km/h, slope 10%). Besides catecholamine concentrations in plasma, as an index of alpha-receptor-stimulation potassium concentrations in plasma were determined. Immediately after exercise, plasma noradrenaline was increased from 310 to 579 pg/ml, plasma adrenaline from 136 to 222 pg/ml and plasma potassium from 4.23 to 4.6 mmol/l. After beta-adrenoceptor blockade exercise caused a significantly higher increase in plasma noradrenaline from 352 to 755 pg/ml and plasma adrenaline from 172 to 260 pg/ml. Also plasma potassium concentrations were significantly elevated from 4.03 to 5.05 mmol/l. The results indicate an enhanced reflex activation of sympatho-neuronal and sympatho-adrenal mechanisms during exercise after beta-adrenoceptor blockade; the increased concentrations of noradrenaline at the adrenoceptors might reduce the efficiency of beta-blockade. Concomitantly, increased stimulation of alpha-adrenoceptors is elicited, which becomes obvious by an increase of potassium concentration in plasma.
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