A simple and specific determination of trypsin in human duodenal juice

A simple and specific method for the estimation of trypsin in human duodenal juice was described. The procedures are as follows: add 10 ul of undiluted sample, measure 2.0 ml of substrate solution of benzoylarginine p-nitroanilide (BAPNA) 0.5 mg/ml in a Tris buffer, incubate at 37 degrees C for 10 minutes, then terminate tryptic activity with 2.0 ml of 30% v/v acetic acid, and read absorbance at 410 nm by a spectrophotometer. Coexistence of bile pigments, chymotrypsin or elastase did not interfere the estimation of tryptic activity in duodenal juice. Reproducibility (both within- and between-assay variances less than 8%), recovery (mean of 100%) and stability of the enzyme activity after 3 weeks at -20 degrees C with glycerol (96% of the initial activity) were sufficient for clinical use. The amidase activity of trypsin estimated with BAPNA as substrate correlated well both to the esterase activity measured with p-toluenesulfonyl-L-arginine methyl ester (TAME) as substrate and to the immunoreactivity determined by radioimmunoassay in human duodenal juice. Good correlation between total outputs of amylase and trypsin were observed in 29 patients undergoing pancreozymin secretin test. The present assay technique will provide simple and reliable means of measuring trypsin in duodenal fluid and of mutual checks of the secretory capacity of pancreatic enzymes and will increase diagnostic accuracy of pancreozymin secretin test.