Radioimmunological quantitation of the urinary trypsin inhibitor in normal blood and urine.

A radioimmunoassay for measurement of the urinary trypsin inhibitor in human serum and urine is described. Because of the immunological cross-reactivity between the inter-alpha-trypsin inhibitor and the urinary trypsin inhibitor the plasma and serum were treated with perchloric acid to precipitate the inter-alpha-trypsin inhibitor. Gel filtration of serum before and after acid treatment showed identical peaks corresponding to the urinary trypsin inhibitor. The normal level of the urinary trypsin inhibitor in fresh plasma from 30 blood donors was 6.38 +/- 0.33 mg/l (SEM), and in sera from 24 healthy volunteers 7.14 +/- 0.27 mg/l (SEM). In urine from 23 healthy volunteers the normal excretion was 8.17 +/- 1.18 mg/24 h (SEM).