Method for measuring the concentration of protease inhibitors, kit for

Abstract

This invention provides a method for measuring the concentration of urinary trypsin inhibitors which is excellent in precision and reproducibility, whose operation is simple, and in which a possibility of damaging a plastic cell is eliminated. The method for measuring the concentration of urinary trypsin inhibitors comprises mixing an urine sample, a protease solution containing trypsin, and a buffer solution, adding a substrate solution to the mixture to cause the enzyme reaction, and measuring the activity of the enzyme, wherein the buffer solution is prepared so that it contains at least 0.15 .mu.mol calcium per 1 .mu.g of the trypsin but no more than 100 .mu.mol calcium per 1 ml of the urine sample in the reaction mixture, and wherein the substrate solution is prepared by dissolving the substrate in an organic solvent and diluting the mixture solution with aqueous medium, wherein at least one of an amphoteric surfactant and a nonionic surfactant is added to at least one of the organic solvent and the aqueous medium.