Appearance of atrial natriuretic peptide in the ventricles in patients with myocardial infarction

To study whether atrial natriuretic peptide (ANP) is present in the ventricles in patients with myocardial infarction, we have examined ventricular tissues from five patients with myocardial infarction and five control subjects without cardiovascular diseases by the indirect immunoperoxidase method using monoclonal antibody to alpha-human ANP. Immunoreactivity for ANP was observed in the subendocardial cardiac cells of infarcted as well as noninfarcted segments of the left ventricles in all patients with myocardial infarction. In a case of biventricular infarcts, the subendocardial cardiac cells of the right ventricle were also stained. In a case of ventricular aneurysm, the viable hypertrophied cardiac cells were immunoreactive for ANP throughout the wall of the aneurysm. Immunoreactivity for ANP, however, was not detected in the working ventricular cardiac cells in any of the control subjects. Because ANP improves left ventricular function by reducing both preload and afterload, the appearance of ANP in the ventricles in patients with myocardial infarction may be one of the manifestations of the compensatory mechanism.