Turnover of fibrinopeptide A (FPA) in rabbits

FPA disappeared from the circulating blood along a double-exponential decay curve consisting of an initial phase (t 1/2 = 1.8 min) and a late phase (t 1/2 = 34.7 min). The rapid decrease in blood FPA was due to the large extravascular space, the size of which was estimated to be about 5 times larger than that of intravascular space. The actual amounts of 125I-FPA distributed to the organs and tissues were generally quite low. However, in the case of the urine, the injected amount of FPA was excreted at the rate of 50% per hour. Thus, the urinary FPA levels may reflect the occurrence of intravascular coagulation.