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

A highly sensitive radioimmunoassay for alpha-human atrial natriuretic peptide (alpha-hANP) was established and applied to measure the human plasma alpha-hANP levels. In our assay system, anti-alpha-hANP antiserum was raised in albino rabbits by intradermally injecting synthetic alpha-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 alpha-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 alpha-hANP (i alpha-hANP) in normal subjects were 24.8 +/- 2.1 pg/tube. In patients with chronic renal failure undergoing hemodialysis, the averaged plasma i alpha-hANP levels were 56.4 +/- 5.0 pg/ml before hemodialysis. Plasma i alpha-hANP levels were significantly higher in the patients with chronic renal failure than in the normal subjects. After hemodialysis, plasma i alpha-hANP levels decreased significantly (32.2 +/- 2.8 pg/ml). These results suggest that the alteration in extracellular fluid volume (ECFV) may affect the plasma levels of i alpha-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 alpha-hANP.