Positive inotropic effect of manganese on dog myocardium

Abstract

Intravenous manganese chloride (25-100 mg) produced an increase in myocardial contractile force in dogs subjected to thoracotomy, bilateral vagotomy. total spinal anesthesia, and pretreatment with reserpine. The positive inotropic effect of Mn was abolished by beta adrenergic blockade with pronethalol and by bilateral adrenalectomy. It appeared later than a similar effect produced by isoproterenol and was preceded by a fall in blood pressure possibly due to vasodilatation. An increase in heart rate and widening of the pulse pressure were observed during the peak inotropic effect. It is concluded that the positive inotropic effect of Mn is due to stimulation of the adrenal medulla by this cation and subsequent release of catecholamines from the adrenal gland.