A highly sensitive radioimmunoassay of atrial natriuretic peptide (ANP) in human plasma and urine.

A highly sensitive radioimmunoassay has been established for measurement of human plasma and urine concentrations of atrial natriuretic peptide (ANP) and requires no extraction or concentration process such as Sep-Pak C-18 cartridge treatment. An antiserum was prepared from rabbits immunized with alpha-human ANP (alpha-hANP) coupled with bovine-thyroglobulin. The sensitivity of this method was 0.3 pg/tube of synthetic alpha-hANP utilized as authentic standard. Recovery of alpha-hANP spiked to plasma and urine was 97.7 +/- 15.4% and 97.1 +/- 9.5% (mean +/- SD), respectively. Plasma and urinary ANP concentrations versus assay data showed satisfactory linearity. In 124 healthy subjects, the plasma ANP-concentration was 31.7 +/- 12.0 pg/ml. Two different molecular forms of ANP in plasma and a single form in urine were found by gel permeation chromatography.