On the origin of urinary fibrinopeptide A (FPA)

Abstract

We have already reported on the measurement of urinary FPA. The purpose of this study is to clarify the origin of the urinary FPA.1. Tracer study using 125I-FPA gave the following results: 1) The disappearance curve of 125I-FPA from blood showed the following equation, X=78.8e-0.531t+19.4e-0.0175twhere: X is the FPA (%) remained in blood at the time t (min.). 2) The disappearance rate of 125I-FPA from blood to extravascular space was very fast. The rapid component of this equation gave 1.8min. of half life of FPA. 3) The blood FPA appeared in urine 5min. after injection. The accumulated FPA in urine for 1hr reached to 40% of the injected FPA.2. The study of organ distribution of 125I-FPA at 1hr after injection showed less than 10% of total FPA mainly in liver and kidney.3. The fibrinogen added to urine gave no increased level of FPA. The immunoreactivity of FPA in urine was not significantly changed by the incubation for 24hr at 37°C. The possibility for decomposition and generation of FPA in the urinary tract was, therefore, found to be negative.In conclusion, although the determination of FPA level in plasma is a direct evidence for the generation of thrombosis, our results showed that the FPA level can not be a diagnostic proof for estimating the size of thrombi, since plasma FPA was excreted rapidly into urine. The measurement of urinary FPA may suggest a possibility for the detection of intravascular thrombosis.