THE N-TERMINUS OF THE ATRIAL-NATRIURETIC-FACTOR PROHORMONE IN THE PLEURAL FLUID OF CONGESTIVE HEART-FAILURE PATIENTS

To investigate the possibility that the prohormone of atrial natriuretic factor might be secreted into the pleural fluid of patients with congestive heart failure who are known to have high concentrations of both the N-terminus and C-terminus of this prohormone circulating in their plasma, six patients with class 2 New York Heart Association classified congestive heart failure had the simultaneous measurement of plasma and pleural fluid N-terminal and C-terminal atrial natriuretic factor prohormone concentrations. The 98 amino acid (aa) N-terminus, the midportion of the N-terminus consisting of aa 31-67 of the 126 aa ANF prohormone (ie, pro ANF 31-67), and the C-terminus (aa. 99-126, ANF) were found in high concentrations in the pleural fluid of all of these patients. The concentrations of the N-terminus (ie, pro ANF 1-98), and pro ANF 31-67 in pleural fluid were nearly equal to their concentration in plasma of these patients. Their plasma levels were more than double the plasma concentrations of pro ANFs 1-98 and 31-67 in 54 persons without congestive heart failure. These preliminary findings demonstrate that all 126 amino acids of the ANF prohormone are present in pleural fluid of patients with congestive heart failure since both the 98 aa N-terminus and the C-terminus (aa 99-126) are present. Whether or not the N-terminus, which contains diuretic and natriuretic peptides, secretion into pleural fluids helps clear the fluid present in the lung in congestive heart failure could not be determined from the present investigation.