MYOCARDIAL CATECHOLAMINE AND NEUROPEPTIDE-Y DEPLETION IN FAILING VENTRICLES OF PATIENTS WITH IDIOPATHIC DILATED CARDIOMYOPATHY - CORRELATION WITH BETA-ADRENERGIC-RECEPTOR DOWN-REGULATION

Background. Myocardial adrenergic neurotransmitters and beta-adrenergic receptor levels were measured in left and right ventricular myocardial specimens obtained from 30 patients with biventricular failure resulting from idiopathic dilated cardiomyopathy. Methods and Results. Nonfailing myocardium obtained from 12 organ donors provided control data. Norepinephrine, dopamine, and neuropeptide Y concentrations were significantly decreased in failing compared with nonfailing control hearts. The mean ratio of dopamine to norepinephrine and of dopamine to neuropeptide Y in failing hearts was also significantly decreased compared with nonfailing control hearts. Compared with nonfailing control hearts, B(max) and beta(1)-receptor density were significantly decreased in failing hearts and there were weak but significantly positive correlations of B(max) and beta(1)-adrenergic receptors with norepinephrine, dopamine, and neuropeptide Y. Conclusions. Norepinephrine and its cotransmitter neuropeptide Y are depleted in failing human ventricular myocardium. Decreased norepinephrine stores correlate weakly with beta(1)-adrenergic receptor downregulation consistent with the hypothesis that norepinephrine depletion occurs in response to increased adrenergic drive. Decreased dopamine relative to norepinephrine implies that an abnormality of dopamine conversion to norepinephrine is not present in failing human heart.