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Fibrinopeptide A (FPA) in both urine and plasma was measured using radioimmunoassy in order to confirm the presence of intrarenal coagulation in renal disease. Patients were divided into 2 groups according to the urinary FDP (mg)/urinary protein (g) ratio: Group A, patients with above 1.0 of the ratio. Group B, patients with less 0.5 of the ratio.The results were as follows: (1) Urinary FPA did not correlate to plasma FPA. (2) Urinary FPA were significantly high in group A, but were normal in group B. (3) The renal functions of group A were all markedly deteriorated. But, the renal functions of group B showed widely spread values. (4) Heparin administration on group A patients reduced their urinary FPA with improvement of renal functions and azotemia.These results indicate: (1) Above 1.0 of urinary FDP (mg)/urinary protein (g) ratio and high urinary FPA reflect the presence of extensive intrarenal coagulation. (2) Extensive intrarenal coagulation was occured only in the patients with markedly deteriorated renal functions. (3) These patients were only a few in renal disease patients. (4) It might be difficult to get good clinical improvement in chronic patients even when intrarenal coagulation is both accuratetly detected and completely eliminated by anticoagulants. (5) However, anticoagulant therapy has proved to be benificial in acute pacients with extensive intrarenal coagulation.

Fibrinopeptide A (FPA) is a peptide released from N-terminal ends of Aα chain of fibrinogen molecule in initial stage of fibrinogen-fibrin conversion. It is, therefore, considered that the determination of FPA in blood or urine is able to be a direct proof of fibrin formation occuring in vivo.The authors studied the radioimmunoassay of FPA of blood and urine in normal adults as well as in patients with renal diseases. In determination of FPA, FPA-antiserum, standard FPA and tyrosyl-FPA obtained from IMCO. Co. Ltd. (Sweden) were used. Procedure of FPA assay was accorded with the method developed by Nossel, et al.. The authors ascertained by preliminary experiment that the Nossel's method could be applied to urinary FPA determination. Our results indicated that, 1) FPA values in clotting reflected strongly to thrombin action. A certain level of FPA-immunoreactivity of fibrinogen split products by plasmin (FgDP) was recognized. In purified in-vitro system, FPA-immunoreactivity of FgDP was 20% when compared to the fibrin clotting system of 100%. While, almost negative (0.3%) immunoreactivity was observed in fibrin split products by plasmin (FDP). 2) Mean and range of blood FPA values of 30 normal adults was 0.3±0.4ng/ml, and this was well closed to the values reported by Nossel, et al.. 3) Urinary FPA values of 33 normal adults were 0.8±0.7ng/ml. It was noted that the urinary FPA of patients with renal deseases showed higher values in many cases in contrast to the normal urine.