The N-Terminus of the Atrial Natriuretic Factor Prohormone in the Pleural Fluid of Congestive Heart Failure Patients: Discussion (Part 1)

In: Congestive Heart Failure

2 Nov 2012

The present investigation demonstrates that the whole N-terminus (ie, aa 1-98) of the 126 aa ANF prohormone is present in pleural fluid of patients with congestive heart failure. With the previous demonstration that the C-terminus (ie, ANF, aa 99-126) is present in pleural fluid, it is now evident that all 126 aa of the ANF prohormone are present in the pleural fluid of congestive heart failure patients. Whether the whole prohormone is secreted intact into the pleural fluid or if the prohormone has been proteolytically cleaved into the C-terminus and N-terminus, with further proteolytic processing to form pro ANF 31-67 prior to secretion into the pleural fluid cannot be determined with certainty from the present investigation. If secreted as an intact prohormone, it is obvious, however, from the data of the present investigation that the proteolytic processing to form ANF and pro ANF 31-67 is very rapid as the concentration of pro ANF 31-67 from the midportion of the N-terminus is very high in pleural fluid and almost equal to its concentration in plasma. The C-terminus (ANF), likewise, is present in high concentration in the pleural fluid of these patients, indicating that it also has been cleaved off the intact prohormone. Thus, if the whole prohormone is secreted intact into pleural fluid, it is rapidly processed proteolytically to cleave off* aa 99126 (ANF) and to form pro ANF 31-67. The formation of pro ANF 31-67 suggests that other peptides on either side of pro ANF 31-67 in the N-terminus consisting of amino acids 1-30 and aa 68 to 98 or smaller fragments thereof are also in the pleural fluid since the intact 1-98 aa N-terminus from which they would be formed was found in pleural fluid in the present investigation. The exact amino acid length of these other peptides from the N-terminus has not been determined at present.


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