The purpose of this paper is to investigate in vitro the inhibitory effects of FOY against the consumption in blood component during extracorporal circulation. Normal citrated intact or contact plasmas were used as materials. Three glass beads columns for measurement of blood platelet retention were used with straight connection as a model of extracorporal circulation, and 3 ml of intact plasmas were passed through the column for 5 minutes. Before and after the filtrations, the changes of

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... ification time (RT), PTT, act. PTT, contact factor, Factor Xa, plasma kallikrein and AT III were tested as parameters. The results were obtained as follows : 1) The inhibitory effects of FOY on the first phase in blood coagulation were shown at the concentration of 10-4M or more. 2) The duration time of FOY was extremely short as several minutes. 3) Act. PTT were prolonged significantly when FOY was added to intact plasma. 4) RT and PTT were prolonged by the action of FOY on Factor XII or Factor XI deficient plasma as substrate, and after filtration, the inhibitory effects of FOY on Factor XII activity was more dominant than that of Factor XI. 5) The elevations in activity of Factor Xa and plasma kallikrein after filtration were protected by FOY, and its action was more effective to the latter. 6) AT III was consumed during filtration, however, the change was remained to be slight by the addition of FOY. These results suggest that F Y as activities o anti-conf act factor, antiplasma kallikrein, and anti-Factor Xa, but the duration time is very short.