Abstract

BACKGROUND--C-type natriuretic peptide (CNP) is a recent addition to the family of natriuretic peptides which includes atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP). Whilst the levels of ANP and BNP are increased in conditions such as congestive heart failure and cor pulmonale, abnormal levels of CNP in these conditions have not been reported. METHODS--Plasma levels of CNP were measured by specific radioimmunoassay in 12 young normal controls, 12 elderly normal controls, 12 patients with NYHA grade III-IV congestive heart failure, and in 16 patients with hypoxaemic cor pulmonale. RESULTS--Mean (SE) plasma levels of CNP were similar in young normal controls (0.46(0.03) pmol/l), elderly normal controls (0.43(0.05) pmol/l), and in patients with congestive heart failure (0.33(0.2) pmol/l). In patients with cor pulmonale, however, plasma levels of CNP were raised (1.39(0.27) pmol/l) 3.2-fold compared with age-matched controls. CONCLUSIONS--In cor pulmonale the increased plasma levels of CNP were not as great as the previously observed increases in levels of ANP (5.6-fold) or BNP (18.5-fold) in comparable patients. CNP may therefore be less important than ANP or BNP as a circulating counter-regulatory peptide in conditions of overactivity of the renin angiotensin system.