ANP now belongs to a family of natriureteic peptides that also includes BNP (brain
natriuretic peptide) and CNP (C-type natriuretic peptide). BNP and CNP have different
N- and C-termini to ANP. CNP has a shorter N-terminal than either ANP or BNP. CNP
has less natriuretic and diuretic activity than ANP or BNP.
ANP receptorshave been isolated and characterized. Three receptor subtypes,
termed ANPA, ANPB, and ANPC, have been described. The ANPAreceptor is a 120 kDa
protein with ANP and BNP as its primary ligands; the ANPBreceptor has CNP as its
primary ligand. The ANPAand ANPBreceptors are coupled to guanylyl cyclase; the
ANPCreceptor is not.
The natriuretic peptides have a short t1/2when administered systemically. They are
rapidly metabolized by the neutral endopeptidase (NEP) enzyme. When ANP is admin-
istered, there is a prompt and profound increase in urine flow and sodium excretion,
HORMONES AND THEIR RECEPTORS 377