Radioimmunoassay for human pancreatic secretory trypsin inhibitor: measurement of serum pancreatic secretory trypsin inhibitor in normal subjects and subjects with pancreatic diseases.

A reliable radioimmunoassay (RIA) for human pancreatic secretory trypsin inhibitor (PSTI) has been developed. The method is highly sensitive (0.4 ng/ml), reproducible and specific. A good parallel relationship was observed between the standard curve and dilution curves for serum and urine. The PSTI bound to trypsin-alpha 2-macroglobulin complexes was found not to be immunoreactive, whereas a part of the psti-trypsin complex was immuno-reactive. In healthy individuals, serum PSTI level ranged from 5.4 ng/ml to 16.0 ng/ml, the average being 11.3 ng/ml (S.D. +/- 2.7). Elevated values were observed in patients with acute pancreatitis (highest value 3200 ng/ml), and in some patients with chronic relapsing pancreatitis.