Urinary immunoreactive brain natriuretic peptide in patients with renal disease

Urinary immunoreactive brain natriuretic peptide (BNP) was studied by radioimmunoassay in patients with renal disease. Urinary immunoreactive human BNP excretion measured in 11 normal subjects was 3.82 ± 0.62 pmol/day (mean ± SEM). Significantly increased 24-h urinary secretion of immunoreactive human BNP was noted in patients with chronic renal failure (11.07 ± 1.73 pmol/day, n = 9, P < 0.05 to normal subjects). A significant correlation was noted between 24-h urinary excretion of immunoreactive human BNP and creatinine clearance in patients with various renal diseases (r = -0.43, P < 0.01, n = 45). Gel chromatography of the urine extracts obtained from normal subjects and patients with chronic renal failure showed multiple immunoreactive peaks; two eluting earlier, one in the position of human BNP-32 and others eluting later. Reverse-phase high-performance liquid chromatography of the urine extracts showed a peak in the position of human BNP-32 and a peak eluting earlier. These findings indicate that: (1) immunoreactive human BNP is present in human urine; (2) urinary immunoreactive human BNP consists of multiple components, i.e., human BNP-32 itself or a substance very similar to it, smaller molecular forms which are probably metabolic products of human BNP-32, and larger molecular forms; and (3) 24-h urinary excretion of immunoreactive human BNP is increased in patients with renal dysfunction.