ProBNP (pro B-type natriuretic peptide) is secreted by cardiomyocytes in response to stretch and is quickly cleaved into 2 circulating fragments—the biologically active 32-amino acid C-terminal BNP (B-type natriuretic peptide) and the inert 76-amino acid NT-proBNP (N-terminal pro-BNP). Both fragments are routinely used to aid diagnosis of heart failure, predict outcomes, and to monitor the effects of therapy.
Differences between BNP and NT-proBNP on a biological level
really relate to the fact that one is biologically active as a hormone, BNP,
whereas NT-proBNP is cleared passively from the body and is not biologically
active.
BNP has a much shorter half-life, and NT-proBNP has a longer
half-life. NT-proBNP, as a consequence, circulates in higher concentrations in
the bloodstream, therefore, more likely to be more sensitive for detecting
earlier forms of heart failure because it circulates at somewhat higher levels.
BNP and NT-proBNP are extracted by the kidneys to a
comparable extent of only about 15–20%. The calculated biological half-lives of
BNP range from 13 to 20 minutes and of NT-proBNP from 25 to 70 minutes.
BNP and NT-proBNP are cleared differentially: BNP is actively removed from the bloodstream (binding to clearance receptors and a much lesser extent by enzymatic degradation by neutral endopeptidase) and also has passive clearance mechanisms, including renal clearance; NT-proBNP is cleared more passively by organs with high rates of blood flow (e.g. muscle, liver, kidneys).
Satyendra Dhar MD,
