Automated "Gamma-flo" radioimmunoassay of urinary cyclic AMP

The "Gammaflow" automated assay concept of Brooker et al. (Science 194:270, 1976) has been adapted to the assay for urinary cyclic AMP in patients' samples on the now commercially available Squibb Gamma-FloTM system, a totally automated continuous-flow immunoassay instrument. The instrument aspirates the unknown sample, combines it with radioligand and specific antiserum, incubates the mixture, separates antibody-bound radioligand from free radioligand, counts the radioactivity of the bound ligand, computes the standard curve, and determines subsequent unknown samples by comparison to the standard curve. The urinary cyclic AMP assay we report here is rapid, accurate, and concentrations of cyclic AMP as low as 15 nmol/L can be detected. The assays, which can be done at 60 determinations per hour, are accurate at all dilutions of urine tested and inter-assay (day-to-day) CVs were 3.9% at the midpoint of the standard curve (B/B0 = 0.49).