The radioimmunoassay for human plasma atrial natriuretic peptide--its application to uremic patients.

A highly sensitive radioimmunoassay for α-human atrial natriuretic peptide (α-hANP) was established and applied to measure the human plasma α-hANP levels. In our assay system, anti-α-hANP antiserum was raised in albino rabbits by intradermally injecting synthetic α-hANP which was conjugated with bovine serum albumin. The final antiserum dilution was 1:50, 000. Sensitivity was 2 pg/tube and the 50% intercept was at 28 pg/tube. The plasma α-hANP was extracted using a Sep-Pak C-18 cartridge. According to this procedure, the mean recovery was 73.8 ± 3.4% (mean ± SE). The averaged plasma levels of immunoreactive α-hANP (iα-hANP) in normal subjects were 24.8 ± 2.1 pg/tube. In patients with chronic renal failure undergoing hemodialysis, the averaged plasma iα-hANP levels were 56.4 ± 5.0 pg/ml before hemodialysis. Plasma iα-hANP levels were significantly higher in the patients with chronic renal failure than in the normal subjects. After hemodialysis, plasma iα-hANP levels decreased significantly (32.2 ± 2.8 pg/ml). These results suggest that the alteration in extracellular fluid volume (EGFV) may affect the plasma levels of iα-hANP in patients with chronic renal failure under hemodialysis; i.e., an increase in ECFV elevates and a decrease in ECFV lowers the circulating levels of α-hANP.