A radioimmunoassay for rat pancreatic secretory trypsin inhibitor

A radioimmunoassay for the detection of pancreatic secretory trypsin inhibitor (PSTI) in the rat is described. The sensitivity of the assay enables the specific measurement of this inhibitor in the serum of normal rats. The average base-line value for multiple animal serum specimens taken from fasting female Wistar rats being fed conventional diets was 11.6 +/- 6.2 micrograms/l. The inhibitor existed in its free form in serum, and PSTI immunoreactivity increased significantly within 2 h of the induction of experimental pancreatitis. The present assay will facilitate the study of PSTI in experimental diseases of the pancreas.