Measurement of human urinary kallikrein and evidence for non-kallikrein urinary tame esterases by direct immunoassay and by affinity chromatography

Kallikrein was separated from other p- tosyl- L -arginine methyl ester (TAMe) esterases in human urine by direct affinity chromatography of concentrated fresh pooled urine. Quantitative analysis of total TAMe esterase activity in pooled, fractionated urine indicated that less than one-third was due to urokallikrein and that the remainder was attributable to one or more esterases which lack kinin-generating activity and fail to react with a monospecific anti-urokallikrein serum. Using a radial immunodiffusion assay for human urokallikrein, recovery of purified urokallikrein added to urine was 95 per cent and the coefficient of variation in replicate analyses was 8.4 per cent. When this method was compared with a kinin-generating and a [ 3 H]TAMe esterase method for determination of kallikrein activity in urine, all three assays were well correlated in 50 urine samples from normal subjects in varying states of salt and water metabolism. However, analysis of the regression line of esterase activity on antigen concentration indicated that at least half of the urinary TAMe esterase activity was due to non-kallikrein esterases. The demonstration by direct assay and by separation techniques that at least one-half of the alkaline TAMe esterase activity of urine is not urokallikrein indicates that changes in urinary esterase activity cannot be equated solely with alterations in urokallikrein. A combination of direct immunological and kinin-generating assays should permit accurate evaluation of urokallikrein concentration and activity.