Brain natriuretic peptide: physiological, biological and clinical aspects

Brain natriuretic peptide is one member of the natriuretic peptide family, including also ANP, CNP, DNP and urodilatin. In human, brain natriuretic peptide is mainly secreted by the cardiac ventricles. BNP is synthetized as pre-proBNP form, secondary cleaved in proBNP, itself equimolarly cleaved in BNP and NT-proBNP. The biological action of BNP is mediated by the NPR-A receptor. This peptide is eliminated from the systemic circulation by a neutral endopeptidase and by a clearance receptor (NPR-C). The BNP and NT-proBNP concentrations are measured using automated rapid immunoassay techniques. Plasma concentrations of the two peptides physiologically increase with age and are found to be higher in women than in men. The action of BNP against fluid expansion is explained by its vascular (vasodilatation), renal (diuretic and natriuretic) and cerebral activities. The measurement of these two peptides contributes to the diagnosis of heart failure. These peptides are prognostic markers both in heart failure and in acute coronary syndromes. In renal insufficiency, the interpretation of the increase in these two peptide concentrations may be difficult, particularly with the NT-proBNP which is mainly excreted by the kidneys.