IN VIVO BEHAVIOUR OF FROZEN AND FREEZE-DRIED FIBRINOGEN AND OF THAT PREPARED FROM OUT-DATED BLOOD

1. (1) The effect of freezing and freeze-drying on the metabolic behaviour of fibrinogen has been investigated by double isotope techniques using a differently labelled native aliquot from the corresponding batches of fibrinogen as a control. The results indicated that purified human or rabbit fibrinogen can be frozen and refrozen repeatedly without altering their biological properties. Freezing did not induce aggregation or partial polymerisation and frozen-dried rabbit fibrinogen behaved in vivo indistinguishably from the native protein. 2. (2) Human fibrinogen prepared from a pool of out-dated but properly stored blood was catabolised at the same rate as a simultaneously injected fresh control fibrinogen, except for a small fraction which was obviously denatured. 3. (3) Rabbit, monkey and human fibrinogens appeared to retain their metabolic integrity for at least several weeks when stored frozen at -25°. 4. (4) From a metabolic point of view it is concluded that advance preparations of fibrinogen for establishing frozen pools are permissible. However, to obtain results in vivo beyond doubt, such pools should be run on fibrinogen originating from fresh plasma. © 1969.