C-type natriuretic peptide (CNP) is the major natriuretic peptide in human cerebrospinal fluid

In order to investigate whether C-type natriuretic peptide (CNP) is present in human cerebrospinal fluid (CSF), we measured CNP-like immunoreactivity (-LI) in human CSF by specific radioimmunoassay (RIA) for CNP. We also measured atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) concentrations in human CSF. ANP-LI, BNP-LI, and CNP-LI concentrations of CSF collected from fifteen patients without neurological disorders were 0.20 +/- 0.13, 0.27 +/- 0.10, and 2.13 +/- 0.27 fmol/ml (mean +/- S.D.), respectively. In fifteen patients with neurological disorders, ANP-LI, BNP-LI, and CNP-LI concentrations in CSF were 0.21 +/- 0.18, 0.33 +/- 0.19, and 2.09 +/- 0.82 fmol/ml, respectively. Although ANP-LI and BNP-LI concentrations in plasma were much higher than those in CSF, CNP-LI was undetectable in plasma (less than 0.2 fmol/ml). These results demonstrate that three natriuretic peptides are present in CSF and that CNP is the major natriuretic peptide in human CSF. These results suggest that CNP in CSF is originated from and play important roles in the central nervous system.