RADIOIMMUNOASSAY FOR CIRCULATING HUMAN GUANYLIN

A highly specific and sensitive radioimmunoassay for circulating human guanylin (guanylin-22-115) has been developed. Antibodies were raised against the amino-terminus (positions 4-16) of the peptide. Western b lot analysis confirmed that the antibody selected for radioimmunoassay recognizes circulating high molecular weight (10.3 kDa) guanylin. Ext raction and purification of guanylin from blood hemofiltrate and from blood plasma showed that circulating guanylin is detectable in corresp onding amounts by the radioimmunoassay and by a specific bioassay. In 30 healthy subjects, the mean plasma concentration of immunoreactive ( IR) guanylin was 42 +/- 3 fmol/ml. In 22 patients with chronic renal i nsufficiency, the concentrations of IR-guanylin were significantly enh anced (1,074 +/- 24 fmol/ml), indicating that kidneys metabolize and/o r eliminate the circulating hormone.