Brain natriuretic peptides in human plasma, spinal cord and cerebrospinal fluid.

In cases of heart failure, the plasma level of immunoreactive human brain natriuretic peptide (IR-hBNP) measured by radioimmunoassay increased 6- to 46-fold over normal level (4.1 +/- 1.0 pg/ml), depending upon the severity. These levels did not significantly correlate to the levels of IR-human atrial natriuretic peptide in individuals. A 4-kDa IR-hBNP, corresponding to authentic hBNP (1-32), was predominant in normal plasma. In cases of cardiac disease, larger molecules which were assumed to be precursors of the 4-kDa form were accumulated in plasma. IR-hBNP was detected in spinal cords (7-24 pg/mg protein) and cerebrospinal fluid (8-19 pg/ml) of patients with noncardiac diseases. The major molecular form corresponded to the hBNP (1-32).