Plasma A- and B-type natriuretic peptides: physiology, methodology and clinical use.

1. Introduction smaller fragments some of which may also have biological activity [5]. Less is known about the procession of BNP; it In the 20 years which have passed since the first is believed to be more constitutively expressed. Pro-brain description by de Bold of a natriuretic and diuretic natriuretic peptide is a 108-amino acid peptide also cleaved substance produced in the heart [1], a large body of into equimolar amounts of the 32-amino acid active BNP research has firmly established the position of the heart as and an inactive N-terminal fragment, N-BNP. ANP, BNP, an endocrine organ. Two peptides, both containing a 17-N-ANP and N-BNP all circulate in plasma. In animals, the amino acid ring structure, have been a focus of much structure of the natriuretic peptides is often very different, interest: atrial natriuretic peptide (ANP), and brain (or especially for BNP, which is much less conserved than B-type) natriuretic peptide (BNP). A third member of this ANP. family of peptides, C-type natriuretic peptide, has been The triggering factor for release / production of ANP and described; it is mainly produced by the endothelium and BNP is an increase in stretch and / or pressure, but neuro-not by the heart, has no diuretic or natriuretic activity, and humoral factors such as angiotensin II and endothelin may will not be discussed here. also play a role. Most effects of ANP and BNP are ANP is produced mainly in the cardiac atria, while BNP, mediated through binding to the A-type natriuretic peptide originally isolated from porcine brain, was soon reported receptor, which activates guanyl cyclase, leading to the to be mainly produced in the cardiac ventricles. In recent formation of cyclic guanosine monophosphate (cGMP). years, however, it has become clear that in fact both ANP Clearance of ANP and BNP from the blood is effected in and BNP are produced both in atria and in ventricles, and two ways: through a special clearance receptor, the C-type that ANP is normally predominant; under pathological natriuretic peptide receptor, and through enzymatic degra-conditions production of BNP rises strongly in both atria dation by neutral endopeptidase. The inactive N-terminal and ventricles and plasma concentrations may overtake fragments have no specific clearance receptor. As a result those of (also risen) ANP [2,3]. Both are formed as they have a longer half-life, especially N-ANP, which pre-pro-polypeptides. Pro-atrial natriuretic peptide is a therefore circulates in plasma in much …