A Study of the Cation-and pH-Dependent Stability of Factors V and VIII in Plasma*

Red cell and platelet concentrates from blood collected into half-strength citrate anticoagulant: improved maintenance of red cell 2,3-diphosphoglycerate in half-citrate red cells

This study confirms previous work suggesting equivalent in vitro properties in blood components prepared from donations collected into half-citrate preservative (HCPD) compared to components derived from donations collected into standard citrate-phosphate-dextrose (CPD) preservatives. In addition, red cell products harvested from HCPD donations showed significantly improved maintenance of pH over storage, and this was reflected in improved maintenance of intracellular 2,3-diphosphoglycerate (2,3-DPG). This effect was observed in whole blood and in red cells suspended in a phosphate-containing additive solution (Tuta AAS). Collection into HCPD also improved 2,3-DPG maintenance in red cell concentrates processed following an 18-hour hold at 22 degrees C. These improvements were less pronounced in red cells suspended in a non-phosphate-containing medium (Fenwal Adsol) in which a higher pH was maintained even in units collected in CPD. Platelets harvested from HCPD blood and suspended in plasma showed equivalent quality to platelets from standard donations. Some deterioration of platelet properties was observed when HCPD platelets were stored in a non-citrate synthetic medium. Together with data indicating improved coagulation factor stability, these results suggest that collection into HCPD improves stored blood quality and may also allow logistical benefits in blood component preparation.

Studies on the procurement of blood coagulation factor VIII in vitro studies on blood components prepared in half-strength citrate anticoagulant

The effect of replacing a standard citrate anticoagulant with one containing half the amount of citrate on the in vitro properties of components prepared from blood donations was investigated. This resulted in a significant improvement in factor VIII stability such that there was little loss during overnight storage, and this was reflected in the factor VIII yield in cryoprecipitate. The quality of cellular components in red cell units stored up to 35 days or platelet concentrates stored up to 7 days was not adversely affected. Although initial levels were similar to those in standard anticoagulant, the extent of fibrinopeptide A generation and complement C3 breakdown in red cell units stored for 35 days in half-strength citrate was somewhat increased.

The procoagulant effect of zinc on fibrin clot formation

The influence of Zn+2 on fibrin clot formation was investigated by measuring its effect on the clotting times of fibrinogen exposed to thrombin. It was observed with either human or bovine thrombin that 0.01-0.1 mM Zn+2 induced significant reductions of clotting times in a concentration-dependent manner. The procoagulant effect of Zn+2 occurred in the presence of Ca+2 but was inhibited by metal chelating agents. Higher levels of Zn+2 (greater than 0.2 mM final concentration) were required to accelerate thrombin-induced clot formation in the presence of citrate or oxalate. Similarly with oxalated human plasma, greater than 0.2 mM Zn+2 decreased the clotting time. Cations such as Mg+2 and Mn+2 caused little change in clotting times. As an extension of these findings, we examined the effect of Zn+2 on the inhibition of thrombin by antithrombin-III (AT-III). The presence of as little as 0.006 mM Zn+2 in an incubating mixture of thrombin and AT-III severely reduced the inhibitory activity of AT-III towards thrombin. It was observed that the relative intrinsic fluorescence emission of human thrombin decreased upon exposure to Zn+2 but was unaffected by Mg+2 or Mn+2. It is suggested that Zn+2 can form a complex with thrombin, which results in altered reactivity towards fibrinogen and decreased inhibition by AT-III.

Influence of heparin and calcium chloride on assay, stability, and recovery of factor VIII

The influence of heparin alone or in conjunction with calcium chloride on the coagulation assay for factor VIII, on the stability of factor VIII in blood and in plasma, and on the recovery of factor VIII in cryoprecipitate and in an intermediate purity concentrate was investigated. A stabilizing effect of heparin and calcium on factor VIII activity in blood and plasma could be confirmed. We were, however, unable to make use of the higher activity that can, under certain circumstances, be recovered in the cryoprecipitates; this was mainly due to the poor solubility of cryoprecipitates prepared from heparinized blood. Heparin (or the absence of a calcium chelator) also interferes with the recovery of plasma components other than factor VIII.

Improvement of plasma quality as raw material for factor VIII:C concentrates. Storage of whole blood and plasma and interindividual plasma levels of fibrinopeptide A

Blood collected into different anticoagulants was stored in small tubes at +4 degrees C for up to 26 h. Seven blood coagulation analyses were performed under standardized conditions. High yield and stability of factor VIII:C were found for ACD and CPD-adenine. No changes could be found in the other six parameters tested. Whole blood in blood bags could be stored for 2-4 h at +4 degrees C with maximal yield of F VIII:C, with blood stored overnight the recovery was 65%. In plasma F VIII:C was stable for at least 2 h at room temperature. F VIIIR:Ag and F VIIIR:RCoF were stable in both whole blood and plasma. No activation by plasmin as measured by B beta 15-42 could be demonstrated. The initial FPA levels, reflecting thrombin activation, in the donated blood differed individually and in some blood bags very high concentrations were found. The levels of FPA were not correlated to the time for collection of a bag of blood.

Improved yields of factor VIII from heparinized plasma

The Factor VIII procoagulant activity in plasma, cryoprecipitate, and their polyethylene glycol (PEG) precipitates is markedly increased if blood is collected into heparin rather than into citrate phosphate dextrose (CPD). There is a 34% increase in the initial level of the Factor VIII activity in the heparinized plasma with 78% of this initial activity (184 U) recovered in the cryoprecipitated. As well, the stability of the Factor VIII activity is improved: after 24 h of incubation at 22 degrees C, 99% of the initial activity is retained in heparinized plasma whereas only 64% remains in CPD plasma. The cryoprecipitate prepared from heparinized plasma is equally stable after 24 h. The PEG concentrate prepared from the cryoprecipitate of heparinized plasma is increased to 128 U compared to only 54 U from CPD plasma. Relative recoveries were 531 U/l for heparinized plasma versus 215 U/l for CPD plasma. This represents a 147% increase in yield.

Contribution to the optimal use of human blood. VII. Increase of the yield of factor VIII in four-donor cryoprecipitate by an improved processing of blood and plasma

The influence of different variables on the yield of factor VIII in cryoprecipitate as prepared in the Central Laboratory of the Netherlands Red Cross Blood Transfusion Service, was studied. The following conclusions may be drawn: (1) In case blood should be stored, the use of the anticoagulant solution acid citrate dextrose (ACD) is preferable to citrate phosphate dextrose (CPD) or trisodium citrate (TSC). (2) The temperature of stored whole blood should not decrease below 8 degrees C because of a spontaneous precipitation of factor VIII from blood (and plasma) below this temperature. (3) Cryoprecipitate derived from rapidly frozen plasma (1 min) contains a decreased amount of proteins in comparison with cryoprecipitate prepared from slowly frozen plasma (45 min to 4 h). On the other hand, equal amounts of factor VIII activity were obtained in the precipitate after freezing of plasma at varying rates. (4) Rapid thawing of plasma results in both higher yields of factor VIII procoagulant activity and a higher specific activity of this factor in the resulting cryoprecipitate. (5) The sedimentation of cryoprecipitate is completed after 5 min centrifugation at 1,500 g. (6) At temperatures higher than 8 degrees C, cryoprecipitated factor VIII starts dissolving into the supernatant plasma or in buffer. (7) Factor VIII in lyophilized cryoprecipitate is stable at room temperature. At elevated temperatures it rapidly looses its activity. (8) Evidence was obtained that the improvements which are introduced in the preparation of factor VIII do not lead to a product which is less stable in vitro as well as in vivo.

Immunochemical studies on factor V

Native bovine factor V exhibits a molecular weight of 300000 as determined by gel filtration of untreated plasma. Highly purified factor V exhibits multiple molecular weight forms which range from small active fragments to aggregates of several million which are generated during the purification on cellulose phosphate. Isoelectric focusing on a single high-molecular-weight species produced a single protein and activity peak at pH 4.65. Factor V activity is associated with each protein band observed following polyacrylamide gel electrophoresis. Antisera to factor V prepared in rabbits produces a time-dependent and concentration-dependent inhibition of factor V activity in plasma and purified factor V. The multiple molecular weight forms of factor V appear equivalent upon immunodiffusion and on immunoelectrophoresis migrate as an alpha globulin between albumin and fibrinogen. Immunoprecipitation arcs are equivalent in plasma and serum. Factor V consists of two major types of subunits, a light chain (73000), aggregates of which form the high-molecular-weight species, and a heavy chain (125 000). Using preparations containing one or both chains isolated by disc gel electrophoresis, antiserum was shown to contain two families of antibodies, one against each subunit. Cross reactivity with both light and heavy chain antigens is observed in sheep and goat but not monkey or human plasma. The antisera also neutralized goat and sheep factor V activity.