SYMPATHOMIMETIC EFFECTS OF ACETALDEHYDE ON THE ELECTRICAL AND CONTRACTILE CHARACTERISTICS OF ISOLATED LEFT ATRIA OF GUINEA PIGS

¹ The Ohio State University College of Medicine, Department of Pharmacology, Columbus, Ohio

Acetaldehyde (CH₃CHO), a major metabolite of ethanol, has been postulated to be an indirect-acting sympathomimetic agent. This hypothesis was tested in vitro on the electrically driven left atria of guinea pigs. Simultaneous recordings of transmembrane potentials and isometric contractions were made. CH₃CHO (0.1-30 mM) induced a dose-related biphasic response in the contractile force of the atrium. Low concentrations (0.3-3 mM) induced positive inotropic responses, whereas high concentrations (10-30 mM) induced negative inotropic responses and arrhythmias. Pretreatment with reserpine inhibited the positive inotropic effects induced by CH₃CHO without altering the negative inotropic responses. Propranolol inhibited all inotropic responses induced by CH₃CHO. Low concentrations of CH₃CHO induced changes in the action potential similar to those seen with norepinephrine or tyramine. it was concluded that CH₃CHO induced positive inotropic responses through indirect sympathetic mechanisms and a depression through a direct effect on myocardial tissue.

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