2001.-The expression of adrenomedullin (AM) and atrial natriuretic factor (ANF) were investigated in the myocardium of a rat model of chronic ischemic heart failure (CHF) compared with sham-operated controls. In addition, human myocardium of patients with end-stage heart failure due to idiopathic dilated cardiomyopathy compared with myocardium of normal subjects (NF) was studied. In CHF, similar AM levels but increased ANF expression were observed in left ventricular myocardium, as assessed by semiquantitative PCR. Functional experiments with freshly excised papillary muscles showed no influence of AM on myocardial contractility. In NF human myocardium, the expression of AM mRNA was threefold higher in atrial compared with ventricular tissue. In analogy, ANF mRNA was increased by ϳ15-fold in atrial tissue. In dilated cardiomyopathy, the expression of AM was significantly increased in right and left ventricles compared with NF. In parallel, ventricular ANF expression was enhanced. heart failure; adrenomedullin; myocardial inotropy; atrial natriuretic factor; gene expression PREVIOUS REPORTS DEMONSTRATED that plasma levels of adrenomedullin (AM) are increased in patients with heart failure (12,16,20,23) and ventricular hypertrophy (4). Recent reports suggest that, other than its effects on vascular tone and natriuresis, physiological concentrations of AM may influence myocardial inotropy (7,27). Several groups demonstrated the importance of AM as an auto-and paracrine mechanism for modulation of cellular growth and development (3,8,21,28). As a strong nitric oxide-liberating peptide in the vascular system, systemic and coronary circulation is regulated by AM (5). These results indicate that AM might be involved in the pathophysiology of cardiac hypertrophy and heart failure. Where circulating AM originates from is still debated, but recent data suggest that cardiac AM expression contributes to elevated serum levels in patients with heart failure (9, 29). Under physiological conditions, atrial levels of AM are among tissues of highest expression in the body. High levels of atrial expression (21), its colocalization with the expression of atrial natriuretic peptide, and almost identical physiological actions of AM and atrial natriuretic factor (ANF) (21) led to the hypothesis that, in addition to its local auto-and paracrine effects, AM may also act as a humoral factor of cardiorenal homeostasis.In the present study, gene expression of AM in atrial and ventricular myocardium at two stages of the development of chonic heart failure in spontaneously hypertensive rats (SHR) and idiopathic human heart failure were investigated. Therefore, hearts of SHR with chronic ligation of the left coronary artery as a well characterized model of congestive heart failure (CHF) and myocardium of explanted human hearts with end-stage heart failure due to idiopathic dilated cardiomyopathy (DCM) were investigated. The expression levels of AM were compared with the expression of ANF, a sensitive marker of cardiac hypertrophy and failure....