Development of a urodilatin-specific antibody and radioimmunoassay for urodilatin in human urine.

Urodilatin (URO) (95-126) is a renal-derived natriuretic peptide that is isolated only from human urine. This study describes the development of a URO-specific antibody and a RIA for URO in urine. At present, there is no commonly available URO-specific antibody. We produced a URO-specific antibody without cross-reactivity with atrial natriuretic peptide (ANP) analogs by immunization of rabbits with the URO (95-126) peptide and subsequent purification of the resulting URO antiserum with affinity chromatography with CNBr-activated Sepharose 4B. The urine samples were ethanol-extracted before assay. The CVs were 6.7% (intraassay) and 14.1% (interassay). This study reports the circadian urinary excretion of URO in 24 healthy subjects with seven sampling periods per 24 h.