Radioimmunoassay of secretin in human serum.

A sensitive radioimmunoassay for secretin has been developed. Antisera were raised against synthetic porcine secretin coupled to bovine serum albumin. N-alpha- desaminotyrosyl -beta-alanyl secretin was radioiodinated by a slight modification of the chloramine-T method. Pure synthetic porcine secretin was used as a standard. Free and bound hormone were separated by dextran-coated charcoal. No cross-reactivity was found with structurally and physiologically related peptides. The sensitivity of the assay was high enough to measure fasting secretin levels in human serum. Patients with acute or chronic pancreatitis had mean serum secretin concentration not significantly different from healthy subjects. In patients with pancreatic carcinoma the mean serum secretin concentration was significantly lower than in healthy subjects, although a wide overlap of the two groups was evident.