Abstract
Summary
Hearts isolated from rabbits infused in vivo with norepinephrine were found to be 5-8 times less reactive (positive inotropic effects) to epinephrine, norepinephrine and isoproterenol than were hearts removed from animals similarly infused with saline. Mean non-stimulated contractile force, but not mean spontaneous heart rate, was found to be significantly depressed in hearts from the norepinephrine-infused animals. Negative inotropic and chronotropic responses to acetylcholine were unaltered. Performance of hearts from norepinephrine-infused animals did not improve with time up to 60 min after isolation. Hearts from non-infused animals were infused in vitro with epinephrine or norepinephrine and showed alterations in reactivity similar to those observed with hearts from animals infused in vivo with norepinephrine. The results suggest that the infused catecholamines interact directly with mammalian hearts to produce persistent metabolic or pathologic alterations in reactivity.
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