An improved method for the measurement of rat tissue kallikrein using a monoclonal antibody which recognizes only...

We have used a monoclonal antibody which recognizes active kallikrein to develop a method for measurement of inactive and active kallikrein in rat urine. The inactive kallikrein levels were calculated from the difference between values before and after trypsin pretreatment in the kallikrein direct radioimmunoassay. In this assay, the final dilution of ascitic fluid containing monoclonal antibody was 1:1.6 X 10(7) which gave 35% specific binding to 125I-labelled kallikrein, and the minimal detectable amount was 0.08 ng/tube. When inactive kallikrein was assessed by this method and a kininogenase assay in 23 randomly collected urines, a significant correlation was observed between the values obtained from the two assays (p less than 0.01). The regression line for this relation was similar to that observed between purified active kallikrein concentration and kininogenase activity. The active and inactive kallikrein excretion rates and the inactive/total kallikrein ratio in rats on normal sodium diet were 74.0 +/- 17.3 micrograms/day (m +/- SD), 82.8 +/- 14.4 micrograms/day and 53.1 +/- 7.1%, respectively. This method can now be applied to studies of prokallikrein activation.