Appearance mechanism and molecular heterogeneity of serum pancreatic secretory trypsin inhibitor (PSTI).

Serum immunoreactive pancreatic secretory trypsin inhibitor (PSTI) was measured by RIA. Serum PSTI levels were elevated in case of acute pancreatitis (15 of 15 cases: 317.7 +/- 155.6 ng/ml: Mean +/- SE) or pancreatic carcinoma (16 of 25 cases; 71.8 +/- 17.1 ng/ml), and in those with chronic renal failure (6 of 6 cases: 412.8 +/- 98.2 ng/ml). The molecular heterogeneity of elevated serum PSTI n such diseases was studied using chromatofocusing column chromatography. The results showed that serum PSTI was free from trypsin(-ogen) and was composed of at least three molecular forms of different isoelectric points. Two major forms were eluted around pH 8.2 (peak I) and 7.5 (peak II), with one minor form around pH 6.9 (peak III) from the column. The relative ratio of three forms differed with the disease state. Peak I was high in patients with pancreatic carcinoma, and peak II was high in patients with acute pancreatitis.