Measurement of the Proteinase Inhibitors of the Bovine Pancreas by Radioimmunoassay

Bovine pancreas contains two polypeptide trypsin inhibitors that
are not homologous and differ in their inhibitory activity towards
chymotrypsin, kallikrein, elastase, and other serine proteinases.
The Kunitz inhibitor and the Kazal inhibitor are present in
approximately equimolar concentrations in bovine pancreatic tissue,
yet only the Kazal inhibitor is detectable in the pancreatic juice.
The Kazal inhibitor has been named the pancreatic secretory trypsin
inhibitor, PSTI because its concentration in the pancreatic juice
parallels that of the exocrine secretory proteins. The Kunitz
inhibitor is considered the intracellular inhibitor, however, no
direct information is available concerning the intracellular
localization of these inhibitors in the pancreas. The preparation
of /sup 125/I-labeled derivatives of Kazal and Kunitz inhibitors by
the lactoperoxidase method and a radioimmunoassay for each
inhibitor are described.