[Specificity of the determination of urinary kallikrein activity using an amidolytic assay]

The specificity of a method for the determination of the urinary kallikrein activity based on the amidolytic hydrolysis of the synthetic substrate H-D-valyl-leucyl-arginine-p-nitroanilide has been studied. Results show a good specificity for kallikrein. The amidolytic activity was totally inhibited by aprotinin. The urinary amidolytic activity showed identical dependence on changes in the ionic strength and pH of the incubation medium as the highly purified kallikrein. The sensitivity of the assay was 0.6 nkat/l. The intra-assay coefficient of variation was 4% and the inter-assay coefficient of variation was 10%. The percentage of recovery was between 100 and 110% indicating that no activators or inhibitors of the kallikrein activity on this substrate were present in the urinary samples. Values obtained in presumably healthy subjects were 0.14 +/- 0.08 pkat/s in man (range: 0.05 - 0.27 pkat/s) and 0.49 +/- 0.11 pkat/s in rat (range: 0.35 - 0.58 pkat/s).