B-type natriuretic peptide forms within the heart, coronary sinus, and peripheral circulation in humans: evidence for degradation before secretion.

Background: The B-type natriuretic peptides (BNP and N-terminal pro-BNP) are secreted by the heart and, in the case of BNP, serve to maintain circulatory homeostasis through renal and vascular actions and oppose many effects of the renin-angiotensin system. Recent evidence suggests that in patients with severe heart failure, circulating immunoreactive BNP is made up mainly of metabolites that may have reduced bioactivity. We hypothesized that BNP may be degraded before it even leaves the heart.