Monoclonal antibodies were raised against human pancreatic stone protein (PSP) and used for one-step enzyme immunoassay (EIA). PSP-S2-5 was employed as the standard in the assay. The assay's measurable range was 25-1,500 ng/ml and within run coefficient of variation was 3.7-6.4%. Analytical recovery of the assay was 101.5 +/- 5.65% (mean +/- SD). The results of experiments in which serum was fractionated by Mono S (cation exchange chromatography) suggested that most of immunoreactive material in human serum is PSP-S2-5. The EIA offers simple, rapid, and specific analysis of serum PSP level for clinical diagnosis.

In order to study the concentration of pancreatic stone protein (PSP) in human pancreatic juice, we investigated the influence of the insoluble form of PSP-S1 converted from PSP-S2-5 on PSP determination and the assay method for PSP-S1 precipitate after solubilizing PSP-S1. When bovine trypsin was added to pancreatic juice, PSP-S1 was converted from PSP-S2-5 and precipitated about 45-85% after 1 h. The precipitated PSP-S1 was dissolved in 0.1 M sodium acetate buffer, pH 4.0, and the concentration was measured by the enzyme immunoassay, with similar reactivity to PSP-S1 and PSP-S2-5. The proposed method can offer accurate and specific analysis of the PSP level in pancreatic juice. The results of the fractionation of pancreatic juice and duodenal juice on Mono S cation-exchange chromatography suggested that the major component of PSP was PSP-S2-5 in pancreatic juice and PSP-S1 in duodenal juice.