Immunoenzymometric determination of trypsin/alpha 1-protease inhibitor complex in plasma of rats with experimental pancreatitis.

The currently available radioimmunoassays of trypsin measure total immunoreactive trypsin (EC 3.1.1.7), which includes both trypsinogen and alpha 1-protease inhibitor-bound trypsin. Hitherto, the only way to differentiate these two forms of trypsin has been to fractionate them on a gel-filtration column. We describe here a solid-phase immunoenzymometric assay that rapidly measures the amount of cationic trypsin bound to alpha 1-protease inhibitor in the plasma of rats with experimental pancreatitis. The assay specifically measures this complex within the range from 0.2 to 5.0 ng without interference by high concentrations of free alpha 1-protease inhibitor. The high correlation (r = 0.985) of the values obtained by size fractionation and by this assay demonstrates the accuracy of the assay, which is the first single-tube method for determining this form of activated cationic trypsin in plasma.