Identification and distribution of atrial natriuretic polypeptide in ventricular myocardium of humans with myocardial infarction.

The expression of atrial natriuretic polypeptide (ANP) in the ventricles of human hearts with myocardial infarction (MI) was studied immunohistochemically. Immunoreactive myocytes were identified in the ventricular tissues of all of 16 hearts with old MI (both with and without heart failure) and in all five hearts with subacute MI, but not in any of the eight hearts without MI nor in the five with acute MI. In the nonfailing hearts with MI, ANP positive myocytes surrounded the areas of infarction, and were also seen in the subendocardium of the infarcted segment. In the failing hearts with MI, ANP expression was noted in the whole ventricular subendocardial region, in addition to the border of infarcts. The sites of ANP expression corresponded well to those of marked stress attributable to tissue shrinkage or fibrosis due to MI, haemodynamic overload, or both. It thus appears that ANP expression is augmented in human hearts with MI regardless of the presence or absence of heart failure, and it is suggested that regional mechanical stress on the ventricular myocardium, as well as haemodynamic overload, may be very closely associated with ventricular ANP expression.