ANP and BNP

ANP and BNP are members of the natriuretic peptide family. As its name suggests, ANP is primarily released from the atria in response to enhanced stretch. Although first discovered in porcine brain, BNP is found in large quantities in ventricular myocardium. Release of BNP is thought to occur in response to increased ventricular wall stress. ANP and BNP have similar biological properties, which include vasodilatation, natriuresis and diuresis.

ANP and BNP have direct effects on renal function. These include increasing glomerular filtration rate as a consequence of efferent glomerular arteriolar vasoconstriction and afferent vasodilatation. In addition, they directly inhibit sodium reabsorption in the collecting tubules. Both ANP and BNP also inhibit renin and aldosterone release.

Plasma ANP and BNP levels are elevated in patients with chronic heart failure and indeed levels may be used to aid in the diagnosis of heart failure. Furthermore, plasma ANP and BNP are helpful in providing prognostic assessment of patients with heart failure and post myocardial infarction.

In view of the potential beneficial haemodynamic effects of ANP and BNP, there is current interest in the therapeutic manipulation of the natriuretic peptide system in patients with heart failure. This could be achieved by inhibiting their breakdown (neutral endopeptidase inhibitors) or infusing exogenous synthetic peptide.
Reference
Levin ER, Gardner DG, Samson WK. Natriuretic peptides. N Engl J Med 1998;339:321-328

Cowie MR, Struthers AD, Wood DA, et al. Value of natriuretic peptides in assessment of patients with possible new heart failure in primary care. Lancet 1997; 350: 1349-1351