NT-pro ANP (N-terminal proatrial natriuretic peptide)

NT-pro ANP (N-terminal proatrial natriuretic peptide) means N-terminal polypeptide of ANP (atrial natriuretic peptide) precursor. In rough microsome of atrial cells prepro ANP with 149 amino acid residues is first produced, and its signal peptide (23 amino acids) is cut off in Golgi apparatus leaving pro ANP of 126 amino acids, which is stored in secretory granules. Before secretion, N-terminal peptide of 98 amino acids (NT-pro ANP) and C-terminal peptide of 28 amino acids (ANP) are separated. ANP is secreted from the atrium with the stimulation of atrial expansion owing to the increased blood volume and/or increase in intra-atrial pressure. ANP is a ring-shaped peptide, the main targets of which are kidney and blood vessels, and causes potent natriuresis, blood vessel expansion, to lower blood pressure. ANP forms natriuretic peptide family with BNP (B-type Natriuretic peptide) and CNP (C-type Natriuretic peptide). Plasma ANP very rapidly disappears owing to binding with its receptor and so-called clearance receptor (half-life about 100seconds in canine), making its exact measurement difficult. On the other hand, NT-pro ANP, because it does not bind clearance receptor, has a long half life (60–120mins in man), and serves as an excellent marker of ANP secretion. The measurement of NT-pro ANP is expected to be useful in the examination of heart diseases in dogs